Additive manufacturing recoat assemblies including a vacuum and methods for using the same

ABSTRACT

A recoat assembly ( 200 ) for an additive manufacturing system includes a base member ( 250 ) that is movable in a lateral direction, a powder spreading member ( 202, 204 ) coupled to the base member ( 250 ), wherein the base member ( 250 ) at least partially encapsulates the powder spreading member ( 202, 204 ), and a vacuum ( 290 ) in fluid communication with at least a portion of the base member ( 250 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication 61/851,955 filed May 23, 2019, the contents of which arehereby incorporated by reference in their entirety.

BACKGROUND Field

The present specification generally relates to additive manufacturingsystems and, more specifically, to recoat assemblies for additivemanufacturing systems and methods for using the same.

Technical Background

Additive manufacturing systems may be utilized to “build” an object frombuild material, such as organic or inorganic powders, in a layer-wisemanner. Conventional additive manufacturing systems include various“recoat” apparatuses that are configured to sequentially distributelayers of build material, such that a binder material can be depositedand cured to “build” an object. However, conventional recoat apparatusesmay inconsistently distribute build material, leading to variation inthe objects built by the additive manufacturing system. Furthermore, inthe event of breakage of components of conventional recoat apparatusesgenerally requires that the recoat apparatus be removed for repair,thereby increasing contributing to system downtime and increasingoperating costs. Moreover, some conventional recoat apparatusesdistribute build material by fluidizing the build material, and airbornebuild material may be dispersed to other components of the additivemanufacturing system, and may interfere with and/or degrade the othercomponents of the additive manufacturing system.

Accordingly, a need exists for alternative recoat assemblies foradditive manufacturing systems.

SUMMARY

In one embodiment, a recoat assembly for an additive manufacturingsystem includes a base member that is movable in a lateral direction, apowder spreading member coupled to the base member, where the basemember at least partially encapsulates the powder spreading member, anda vacuum in fluid communication with at least a portion of the basemember.

In another embodiment, a method for forming an object includes moving arecoat assembly over a build material a coating direction, where therecoat assembly includes a powder spreading member, contacting the buildmaterial with the powder spreading member, causing at least a portion ofthe build material to become airborne, and drawing airborne buildmaterial out of the recoat assembly with a vacuum in fluid communicationwith the recoat assembly.

In yet another embodiment, additive manufacturing system includes arecoat assembly including a base member that is movable in a lateraldirection, a powder spreading member coupled to the base member, wherethe base member at least partially encapsulates the powder spreadingmember, and a vacuum in fluid communication with at least a portion ofthe base member, an electronic control unit communicatively coupled tothe vacuum, and a build area positioned below the recoat assembly.

Additional features and advantages of the additive manufacturingapparatuses described herein, and the components thereof, will be setforth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the embodiments described herein, including thedetailed description which follows, the claims, as well as the appendeddrawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a conventional additive manufacturingsystems;

FIG. 2A schematically depicts an additive manufacturing system,according to one or more embodiments shown and described herein;

FIG. 2B schematically depicts another additive manufacturing system,according to one or more embodiments shown and described herein;

FIG. 2C schematically depicts an enlarged view of build material of anadditive manufacturing system according to one or more embodiments shownand described herein;

FIG. 3 schematically depicts an embodiment of a recoat assembly of theadditive manufacturing system of FIG. 2A, according to one or moreembodiments shown and described herein;

FIG. 4 schematically depicts another view of the recoat assembly of FIG.3, according to one or more embodiments shown and described herein;

FIG. 5 schematically depicts another view of the recoat assembly of FIG.3, according to one or more embodiments shown and described herein;

FIG. 6A schematically depicts another side view of a recoat assembly,according to one or more embodiments shown and described herein;

FIG. 6B schematically depicts a section view of a recoat assembly,according to one or more embodiments shown and described herein;

FIG. 6C schematically depicts rollers and roller supports of the recoatassembly of FIG. 6B shown in isolation, according to one or moreembodiments shown and described herein;

FIG. 7A schematically depicts a roller support of FIG. 6C in isolation,according to one or more embodiments shown and described herein;

FIG. 7B schematically depicts another view of the roller support of FIG.7A, according to one or more embodiments shown and described herein;

FIG. 7C schematically depicts a strain gauge for use with the rollersupport of FIG. 7A, according to one or more embodiments shown anddescribed herein; and

FIG. 8 schematically depicts another roller support in isolation,according to one or more embodiments shown and described herein;

FIG. 9A schematically depicts another roller support in isolation,according to one or more embodiments shown and described herein;

FIG. 9B schematically depicts another view of the roller support of FIG.9A, according to one or more embodiments shown and described herein;

FIG. 9C schematically depicts a section view of the roller support ofFIG. 9A, according to one or more embodiments shown and describedherein;

FIG. 9D schematically depicts a load cell for use with the rollersupport of FIG. 9A, according to one or more embodiments shown anddescribed herein;

FIG. 10 schematically depicts a roller support coupled to a load celland at least one strain gauge, according to one or more embodimentsshown and described herein;

FIG. 11A schematically depicts another section view of the recoatassembly of FIG. 6B, according to one or more embodiments shown anddescribed herein;

FIG. 11B schematically depicts a perspective view of a recoat assembly,according to one or more embodiments shown and described herein;

FIG. 11C schematically depicts a perspective section view of the recoatassembly of FIG. 11B, according to one or more embodiments shown anddescribed herein;

FIG. 11D schematically depicts a section view of the recoat assembly ofFIG. 11B, according to one or more embodiments shown and describedherein;

FIG. 11E schematically depicts a bottom perspective view of a recoatassembly, according to one or more embodiments shown and describedherein;

FIG. 12 schematically depicts rollers and energy sources of the recoatassembly of FIG. 6B, according to one or more embodiments shown anddescribed herein;

FIG. 13 schematically depicts one embodiment of a layout of the rollersof the recoat assembly of FIG. 6B, according to one or more embodimentsshown and described herein;

FIG. 14 schematically depicts another embodiment of a layout of therollers of the recoat assembly of FIG. 6B, according to one or moreembodiments shown and described herein;

FIG. 15 schematically depicts another embodiment of a layout of therollers of the recoat assembly of FIG. 6B, according to one or moreembodiments shown and described herein;

FIG. 16A schematically depicts a perspective view of a recoat assemblyincluding a cleaning member, according to one or more embodiments shownand described herein;

FIG. 16B schematically depicts a perspective view of a recoat assemblyincluding a cleaning member, according to one or more embodiments shownand described herein;

FIG. 16C schematically depicts a perspective section view of the recoatassembly of FIG. 16B, according to one or more embodiments shown anddescribed herein;

FIG. 16D schematically depicts an exploded view of a cleaning positionadjustment assembly engaged with the cleaning member of FIG. 16C,according to one or more embodiments shown and described herein;

FIG. 17A schematically depicts a top view of the cleaning member and therollers of the recoat assembly of FIG. 3, according to one or moreembodiments shown and described herein;

FIG. 17B schematically depicts another top view of the rollers of therecoat assembly of FIG. 3 and the cleaning member, according to one ormore embodiments shown and described herein;

FIG. 17C schematically depicts a side view of the rollers of the recoatassembly of FIG. 3 and the cleaning member, according to one or moreembodiments shown and described herein;

FIG. 18A schematically depicts a perspective view of a secondarycontainment housing and a vacuum of the recoat assembly of FIG. 3,according to one or more embodiments shown and described herein;

FIG. 18B schematically depicts a perspective view of a primarycontainment housing and a vacuum of the recoat assembly of FIG. 3,according to one or more embodiments shown and described herein;

FIG. 19 schematically depicts a section view of the vacuum and therecoat assembly of FIG. 3, according to one or more embodiments shownand described herein;

FIG. 20 schematically depicts a perspective view of another recoatassembly, according to one or more embodiments shown and describedherein;

FIG. 21 schematically depicts another perspective view of the recoatassembly of FIG. 20, according to one or more embodiments shown anddescribed herein;

FIG. 22 schematically depicts a section view of the recoat assembly ofFIG. 20, according to one or more embodiments shown and describedherein;

FIG. 23 schematically depicts another section view of a recoat assembly,according to one or more embodiments shown and described herein;

FIG. 24 schematically depicts a control diagram of the additivemanufacturing system according to one or more embodiments shown anddescribed herein;

FIG. 25 is a flowchart for adjusting an operating parameter of theadditive manufacturing system, according to one or more embodimentsshown and described herein;

FIG. 26 is another flowchart for adjusting an operating parameter of theadditive manufacturing system, according to one or more embodimentsshown and described herein;

FIG. 27 is a flowchart for moving build material to a build area,according to one or more embodiments shown and described herein;

FIG. 28 schematically depicts a recoat assembly moving build material toa build area, according to one or more embodiments shown and describedherein;

FIG. 29A schematically depicts a recoat assembly moving build materialto a build area, according to one or more embodiments shown anddescribed herein;

FIG. 29B schematically depicts a recoat assembly compacting buildmaterial within the build area, according to one or more embodimentsshown and described herein;

FIG. 29C schematically depicts a recoat assembly moving build materialto a build area, according to one or more embodiments shown anddescribed herein;

FIG. 29D schematically depicts a recoat assembly moving in a returndirection, according to one or more embodiments shown and describedherein; and

FIG. 30 is a flowchart of a method for drawing build material out of arecoat assembly, according to one or more embodiments shown anddescribed herein.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of additivemanufacturing apparatuses, and components thereof, examples of which areillustrated in the accompanying drawings. Whenever possible, the samereference numerals will be used throughout the drawings to refer to thesame or like parts. One embodiment of an additive manufacturing system100 is schematically depicted in FIG. 2A. The additive manifestingsystem may generally include recoat assemblies for spreading buildmaterial in a build area. In embodiments described herein, recoatassemblies include one or more sensors that detect forces acting on therecoat assembly. By detecting forces acting on the recoat assembly,defects may be identified and one or more parameters related to theoperation of the recoat assembly may be adjusted to optimize theperformance of the recoat assembly. In some embodiments, recoatassemblies described herein may include multiple redundant components,such as rollers and energy sources, such that the recoat assembly maycontinue operation in the event of failure of one or more components ofthe recoat assemblies. In some embodiments, recoat assemblies describedherein are in fluid communication with a vacuum that acts to collect andcontain airborne build material. These and other embodiments of recoatassemblies for additive manufacturing systems, additive manufacturingsystems comprising the recoat assemblies, and methods for using the sameare described in further detail herein with specific reference to theappended drawings.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another embodiment. Itwill be further understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

Directional terms as used herein—for example up, down, right, left,front, back, top, bottom—are made only with reference to the figures asdrawn and are not intended to imply absolute orientation unlessotherwise expressly stated.

The phrase “communicatively coupled” is used herein to describe theinterconnectivity of various components and means that the componentsare connected either through wires, optical fibers, or wirelessly suchthat electrical, optical, and/or electromagnetic signals may beexchanged between the components.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order, nor that with any apparatus specificorientations be required. Accordingly, where a method claim does notactually recite an order to be followed by its steps, or that anyapparatus claim does not actually recite an order or orientation toindividual components, or it is not otherwise specifically stated in theclaims or description that the steps are to be limited to a specificorder, or that a specific order or orientation to components of anapparatus is not recited, it is in no way intended that an order ororientation be inferred, in any respect. This holds for any possiblenon-express basis for interpretation, including: matters of logic withrespect to arrangement of steps, operational flow, order of components,or orientation of components; plain meaning derived from grammaticalorganization or punctuation, and; the number or type of embodimentsdescribed in the specification.

As used herein, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to “a” component includes aspects having two or moresuch components, unless the context clearly indicates otherwise.

Embodiments described herein are generally directed to recoat assembliesfor additive manufacturing systems. Additive manufacturing systems maygenerally “build” materials through successive deposition and binding ofbuild material. In conventional additive manufacturing systems,deposition of build material is a difficult, dirty, time-consuming, anderror-prone process. Embodiments described herein are directed to recoatassemblies that deposit build material in a consistent and configurablemanner.

Referring now to FIG. 1, a conventional additive manufacturing system 10is schematically depicted. The conventional additive manufacturingapparatus 10 includes a supply platform 30, a build platform 20, acleaning station 11, and a build head 15. The supply platform 30 iscoupled to a supply platform actuator 32. The supply platform actuator32 is actuatable in the vertical direction (i.e., the +/−Z direction ofthe coordinate axes depicted in the figure) such that the supplyplatform 30 may be raised or lowered. The build platform 20 is locatedadjacent to the supply platform 30 and, like the supply platform 30, iscoupled to an actuator, specifically a build platform actuator 22. Thebuild platform actuator 22 is actuatable in the vertical direction suchthat the build platform 20 may be raised or lowered. The cleaningstation 11 is located adjacent to the supply platform 30 opposite thebuild platform 20. That is, the supply platform 30 is located betweenthe cleaning station 11 and the build platform 20 along the working axisof the conventional additive manufacturing apparatus 10 (i.e., an axisextending parallel to the +/−X axis of the coordinate axes depicted inthe figure). The build head 15 may be traversed along the working axisof the conventional additive manufacturing apparatus 10 with an actuator(not depicted) such that the build head 15 passes from a home position12 co-located with the cleaning station 11 over the supply platform 30,over the build platform 20, and back again, ultimately returning to thehome position 12.

In operation, build material 31, such as organic or inorganic powder, ispositioned on the supply platform 30. The supply platform 30 is actuatedto present a layer of the build material 31 in the path of the buildhead 15. The build head 15 is then actuated along the working axis ofthe conventional additive manufacturing apparatus 10 from the homeposition 12 towards the build platform 20 in the direction indicated byarrows 40. As the build head 15 traverses the working axis over thesupply platform 30 towards the build platform 20, the build head 15distributes the layer of build material 31 in the path of the build head15 from the supply platform 30 to the build platform 20. Thereafter, asthe build head 15 continues along the working axis over the buildplatform 20, the build head 15 deposits a layer of binder material 50 ina predetermined pattern on the layer of build material 31 that has beendistributed on the build platform 20. Optionally, after the bindermaterial 50 is deposited, an energy source within the build head 15 isutilized to cure the deposited binder material 50. The build head 15then returns to the home position 12 where at least a portion of thebuild head 15 is positioned over the cleaning station 11. While thebuild head 15 is in the home position 12, the build head 15 works inconjunction with the cleaning station 11 to provide cleaning andmaintenance operations on the elements of the build head 15 whichdeposit the binder material 50 to ensure the elements are not fouled orotherwise clogged. This ensures that the build head is capable ofdepositing the binder material 50 in the desired pattern during asubsequent deposition pass. During this maintenance interval, the supplyplatform 30 is actuated in an upward vertical direction (i.e., in the +Zdirection of the coordinate axes depicted in the figure) as indicated byarrow 43 to present a new layer of build material 31 in the path of thebuild head 15. The build platform 20 is actuated in the downwardvertical direction (i.e., in the −Z direction of the coordinate axesdepicted in the figure) as indicated by arrow 42 to prepare the buildplatform 20 to receive a new layer of build material 31 from the supplyplatform 30. The build head 15 is then actuated along the working axisof the conventional additive manufacturing apparatus 10 again to addanother layer of build material 31 and binder material 50 to the buildplatform 20. This sequence of steps is repeated multiple times to buildan object on the build platform 20 in a layer-wise manner.

Referring now to FIG. 2A, an embodiment of an additive manufacturingsystem 100 is schematically depicted. The system 100 includes a cleaningstation 110, a build area 124, a supply platform 130, and an actuatorassembly 102. The actuator assembly 102 comprises, among other elements,a recoat assembly 200 for distributing build material 31 and a printhead 150 for depositing binder material 50. The actuator assembly 102 isconstructed to facilitate traversing the recoat assembly 200 and theprint head 150 over the working axis of the system 100 independent ofone another. This allows for at least some steps of the additivemanufacturing process to be performed simultaneously thereby reducingthe overall cycle time of the additive manufacturing process to lessthan the sum of the cycle time for each individual step. In theembodiments of the system 100 described herein, the working axis 116 ofthe system 100 is parallel to the +/−X axis of the coordinate axesdepicted in the figures. It should be understood that the components ofthe additive manufacturing apparatus 100 traversing the working axis116, such as the recoat head 140, the print head 150, or the like, neednot be centered on the working axis 116. However, in the embodimentsdescribed herein, at least two of the components of the additivemanufacturing apparatus 100 are arranged with respect to the workingaxis 116 such that, as the components traverse the working axis, thecomponents could occupy the same or an overlapping volume along theworking axis if not properly controlled.

In the embodiments described herein, the cleaning station 110, the buildplatform 120, and the supply platform 130 are positioned in series alongthe working axis 116 of the system 100 between a print home position 158of the print head 150 located proximate an end of the working axis 116in the −X direction, and a recoat home position 148 of the recoatassembly 200 located proximate an end of the working axis 116 in the +Xdirection. That is, the print home position 158 and the recoat homeposition 148 are spaced apart from one another in a horizontal directionthat is parallel to the +/−X axis of the coordinate axes depicted in thefigures and the cleaning station 110, the build area 124, and the supplyplatform 130 are positioned therebetween. In the embodiments describedherein, the build area 124 is positioned between the cleaning station110 and the supply platform 130 along the working axis 116 of the system100.

The cleaning station 110 is positioned proximate one end of the workingaxis 116 of the system 100 and is co-located with the print homeposition 158 where the print head 150 is located or “parked” before andafter depositing binder material 50 on a layer of build material 31positioned on the build area 124. The cleaning station 110 may includeone or more cleaning sections (not shown) to facilitate cleaning theprint head 150 between depositing operations. The cleaning sections mayinclude, for example and without limitation, a soaking stationcontaining a cleaning solution for dissolving excess binder material onthe print head 150, a wiping station for removing excess binder materialfrom the print head 150, a jetting station for purging binder materialand cleaning solution from the print head 150, a park station formaintaining moisture in the nozzles of the print head 150, or variouscombinations thereof. The print head 150 may be transitioned between thecleaning sections by the actuator assembly 102.

While reference is made herein to additive manufacturing systemsincluding a print head 150 that dispenses a binder material 50, itshould be understood that recoat assemblies 200 described herein may beutilized with other suitable additive powder-based additivemanufacturing systems. For example, in some embodiments, instead ofbuilding objects with a cured binder 50 applied to build material 31, insome embodiments, a laser or other energy source may be applied to thebuild material 31 to fuse the build material 31.

In the embodiment depicted in FIG. 2A, the build area 124 comprises areceptacle including a build platform 120. The build platform 120 iscoupled to a build platform actuator 122 to facilitate raising andlowering the build platform 120 relative to the working axis 116 of thesystem 100 in a vertical direction (i.e., a direction parallel to the+/−Z directions of the coordinate axes depicted in the figures). Thebuild platform actuator 122 may be, for example and without limitation,a mechanical actuator, an electro-mechanical actuator, a pneumaticactuator, a hydraulic actuator, or any other actuator suitable forimparting linear motion to the build platform 120 in a verticaldirection. Suitable actuators may include, without limitation, a wormdrive actuator, a ball screw actuator, a pneumatic piston, a hydraulicpiston, an electro-mechanical linear actuator, or the like. The buildplatform 120 and build platform actuator 122 are positioned in a buildarea 124 located below the working axis 116 (i.e., in the −Z directionof the coordinate axes depicted in the figures) of the system 100.During operation of the system 100, the build platform 120 is retractedinto the build area 124 by action of the build platform actuator 122after each layer of binder material 50 is deposited on the buildmaterial 31 located on build platform 120. While the build area 124described and depicted herein includes a receptacle, it should beunderstood that the build area 124 may include any suitable structurefor supporting build material 31, and may for example include a meresurface supporting the build material 31.

The supply platform 130 is coupled to a supply platform actuator 132 tofacilitate raising and lowering the supply platform 130 relative to theworking axis 116 of the system 100 in a vertical direction (i.e., adirection parallel to the +/−Z directions of the coordinate axesdepicted in the figures). The supply platform actuator 132 may be, forexample and without limitation, a mechanical actuator, anelectro-mechanical actuator, a pneumatic actuator, a hydraulic actuator,or any other actuator suitable for imparting linear motion to the supplyplatform 130 in a vertical direction. Suitable actuators may include,without limitation, a worm drive actuator, a ball screw actuator, apneumatic piston, a hydraulic piston, an electro-mechanical linearactuator, or the like. The supply platform 130 and supply platformactuator 132 are positioned in a supply receptacle 134 located below theworking axis 116 (i.e., in the −Z direction of the coordinate axesdepicted in the figures) of the system 100. During operation of thesystem 100, the supply platform 130 is raised relative to the supplyreceptacle 134 and towards the working axis 116 of the system 100 byaction of the supply platform actuator 132 after a layer of buildmaterial 31 is distributed from the supply platform 130 to the buildplatform 120, as will be described in further detail herein.

In embodiments, the actuator assembly 102 generally includes a recoatassembly transverse actuator 144, a print head actuator 154, a firstguide 182, and a second guide 184. The recoat assembly transverseactuator 144 is operably coupled to the recoat assembly 200 and isoperable to move the recoat assembly 200 relative to the build platform120 to dispense build material 31 on the build platform 120, asdescribed in greater detail herein. The print head actuator 154 isoperably coupled to the print head 150 and is operable to move the printhead 150 and is operable to move the print head 150 relative to thebuild platform 120 to dispense the binder material 50 on the buildplatform 120.

In the embodiments described herein, the first guide 182 and the secondguide 184 extend in a horizontal direction (i.e., a direction parallelto the +/−X direction of the coordinate axes depicted in the figures)parallel to the working axis 116 of the system 100 and are spaced apartfrom one another in the vertical direction. When the actuator assembly102 is positioned over the cleaning station 110, the build platform 120,and the supply platform 130 as depicted in FIG. 2A, the first guide 182and the second guide 184 extend in a horizontal direction from at leastthe cleaning station 110 to beyond the supply platform 130.

In one embodiment, such as the embodiment of the actuator assembly 102depicted in FIG. 2A, the first guide 182 and the second guide 184 areopposite sides of a rail 180 that extends in a horizontal direction andis oriented such that the first guide 182 is positioned above and spacedapart from the second guide 184. For example, in one embodiment, therail 180 has an “I” configuration in vertical cross section (i.e., across section in the Y-Z plane of the coordinate axes depicted in thefigures) with the upper and lower flanges of the “I” forming the firstguide 182 and the second guide 184, respectively. However, it should beunderstood that other embodiments are contemplated and possible. Forexample and without limitation, the first guide 182 and the second guide184 may be separate structures, such as separate rails, extending in thehorizontal direction and spaced apart from one another in the verticaldirection. In some embodiments, the first guide 182 and the second guide184 may be positioned at the same height and spaced apart from oneanother on opposite sides of the rail 180. In embodiments, the firstguide 182 and the second guide 184 are positioned in any suitableconfiguration, and may be collinear.

In the embodiments described herein, the recoat assembly transverseactuator 144 is coupled to one of the first guide 182 and the secondguide 184 and the print head actuator 154 is coupled to the other of thefirst guide 182 and the second guide 184 such that the recoat assemblytransverse actuator 144 and the print head actuator 154 are arranged ina “stacked” configuration. For example, in the embodiment of theactuator assembly 102 depicted in FIG. 2A, the recoat assemblytransverse actuator 144 is coupled to the second guide 184 and the printhead actuator 154 is coupled to the first guide 182. However, it shouldbe understood that, in other embodiments (not depicted) the recoatassembly transverse actuator 144 may be coupled to the first guide 182and the print head actuator 154 may be coupled to the second guide 184.

In the embodiments described herein, the recoat assembly transverseactuator 144 is bi-directionally actuatable along a recoat motion axis146 and the print head actuator 154 is bi-directionally actuatable alonga print motion axis 156. That is, the recoat motion axis 146 and theprint motion axis 156 define the axes along which the recoat assemblytransverse actuator 144 and the print head actuator 154 are actuatable,respectively. The recoat motion axis 146 and the print motion axis 156extend in a horizontal direction and are parallel with the working axis116 of the system 100. In the embodiments described herein, the recoatmotion axis 146 and the print motion axis 156 are parallel with oneanother and spaced apart from one another in the vertical direction dueto the stacked configuration of the recoat assembly transverse actuator144 and the print head actuator 154. In some embodiments, such as theembodiment of the actuator assembly 102 depicted in FIG. 2A, the recoatmotion axis 146 and the print motion axis 156 are located in the samevertical plane (i.e., a plane parallel to the X-Z plane of thecoordinate axes depicted in the figures). However, it should beunderstood that other embodiments are contemplated and possible, such asembodiments in which the recoat motion axis 146 and the print motionaxis 156 are located in different vertical planes.

In the embodiments described herein, the recoat assembly transverseactuator 144 and the print head actuator 154 may be, for example andwithout limitation, mechanical actuators, electro-mechanical actuators,pneumatic actuators, hydraulic actuators, or any other actuator suitablefor providing linear motion. Suitable actuators may include, withoutlimitation, worm drive actuators, ball screw actuators, pneumaticpistons, hydraulic pistons, electro-mechanical linear actuators, or thelike. In one particular embodiment, the recoat assembly transverseactuator 144 and the print head actuator 154 are linear actuatorsmanufactured by Aerotech® Inc. of Pittsburgh, Pa., such as the PRO225LMMechanical Bearing, Linear Motor Stage.

In embodiments, the recoat head actuator 144 and the print head actuator154 may each be a cohesive sub-system that is affixed to the rail 180,such as when the recoat head actuator 144 and the print head actuator154 are PRO225LM Mechanical Bearing, Linear Motor Stages, for example.However, it should be understood that other embodiments are contemplatedand possible, such as embodiments where the recoat head actuator 144 andthe print head actuator 154 comprise multiple components that areindividually assembled onto the rail 180 to form the recoat headactuator 144 and the print head actuator 154, respectively.

Still referring to FIG. 2A, the recoat assembly 200 is coupled to therecoat assembly transverse actuator 144 such that the recoat assembly200 is positioned below (i.e., in the −Z direction of the coordinateaxes depicted in the figures) the first guide 182 and the second guide184. When the actuator assembly 102 is positioned over the cleaningstation 110, the build platform 120, and the supply platform 130 asdepicted in FIG. 2A, the recoat assembly 200 is situated on the workingaxis 116 of the system 100. Thus, bi-directional actuation of the recoatassembly transverse actuator 144 along the recoat motion axis 146affects bi-directional motion of the recoat assembly 200 on the workingaxis 116 of the system 100. In the embodiment of the actuator assembly102 depicted in FIG. 2A, the recoat assembly 200 is coupled to therecoat assembly transverse actuator 144 with support bracket 176 suchthat the recoat assembly 200 is positioned on the working axis 116 ofthe system 100 while still providing clearance between rail 180 of theactuator assembly 102 and the build platform 120 and the supply platform130. In some embodiments described herein, the recoat assembly 200 maybe fixed in directions orthogonal to the recoat motion axis 146 and theworking axis 116 (i.e., fixed along the +/−Z axis and/or fixed along the+/−Y axis).

Similarly, the print head 150 is coupled to the print head actuator 154such that the print head 150 is positioned below (i.e., in the −Zdirection of the coordinate axes depicted in the figures) the firstguide 182 and the second guide 184. When the actuator assembly 102 ispositioned over the cleaning station 110, the build platform 120, andthe supply platform 130 as depicted in FIG. 2A, the print head 150 issituated on the working axis 116 of the system 100. Thus, bi-directionalactuation of the print head actuator 154 along the print motion axis 156affects bi-directional motion of the print head 150 on the working axis116 of the system 100. In the embodiment of the actuator assembly 102depicted in FIG. 2A, the print head 150 is coupled to the print headactuator 154 with support bracket 174 such that the print head 150 ispositioned on the working axis 116 of the system 100 while stillproviding clearance between rail 180 of the actuator assembly 102 andthe build platform 120 and the supply platform 130. In some embodimentsdescribed herein, the print head 150 may be fixed in directionsorthogonal to the print motion axis 156 and the working axis 116 (i.e.,fixed along the +/−Z axis and/or fixed along the +/−Y axis).

While FIG. 2A schematically depicts an embodiment of an actuatorassembly 102 which comprises a first guide 182 and a second guide 184with the recoat assembly transverse actuator 144 and the print headactuator 154 mounted thereto, respectively, it should be understood thatother embodiments are contemplated and possible, such as embodimentswhich comprise more than two guides and more than two actuators. Itshould also be understood that other embodiments are contemplated andpossible, such as embodiments which comprise the print head and therecoat assembly 200 on the same actuator.

Referring to FIG. 2B, in some embodiments, the additive manufacturingsystem 100 comprises a cleaning station 110, and a build area 124, asdescribed herein with respect to FIG. 2A. However, in the embodimentdepicted in FIG. 2B, the additive manufacturing system does not includea supply receptacle. Instead, the system comprises a build materialhopper 360 that is used to supply build material 31 to the build area124. In this embodiment, the build material hopper 360 is coupled to therecoat assembly transverse actuator 144 such that the build materialhopper 360 traverses along the recoat motion axis 146 with the with therecoat assembly 200. In the embodiment depicted in FIG. 2B, the buildmaterial hopper 360 is coupled to the support bracket 176 with, forexample, bracket 361. However, it should be understood that the buildmaterial hopper 360 may be directly coupled to the support bracket 176without an intermediate bracket. Alternatively, the build materialhopper 360 may be coupled to the recoat assembly 200 either directly orwith an intermediate bracket.

The build material hopper 360 may include an electrically actuated valve(not depicted) to release build material 31 onto the build area 124 asthe build material hopper 360 traverses over the build area 124. Inembodiments, the valve may be communicatively coupled to an electroniccontrol unit 300 (FIG. 24) which executes computer readable andexecutable instructions to open and close the valve based on thelocation of the build material hopper 360 with respect to the buildarea. The build material 31 released onto the build area 124 is thendistributed over the build area with the recoat assembly 200 as therecoat assembly 200 traverses over the build area 124.

Referring to FIG. 2C, to form an object layers of build material31AA-31DD may be sequentially positioned on top of one another. In theexample provided in FIG. 2C, sequential layers of binder 50AA-50CC arepositioned on the layers of build material 31AA-31DD. By curing thelayers of binder 50AA-50CC, a finished product may be formed.

Referring to FIG. 3, a perspective view of one embodiment of the recoatassembly 200 is schematically depicted. In embodiments, the recoatassembly 200 may include one or more housings 222, 224 that at leastpartially encapsulate a portion of the recoat assembly 200. The recoatassembly 200 includes the recoat assembly transverse actuator 144 thatmoves the recoat assembly 200 in the lateral direction (i.e., in theX-direction as depicted). In some embodiments, the recoat assembly 200further includes a recoat assembly vertical actuator 160 that moves therecoat assembly 200 in the vertical direction (i.e., in the Z-directionas depicted).

In some embodiments, the recoat assembly 200 includes a base member 250,and the recoat assembly transverse actuator 144 is coupled to the basemember 250, moving the base member 250 in the lateral direction (i.e.,in the X-direction as depicted). As referred to herein the base member250 may include any suitable structure of the recoat assembly 200coupled to the recoat assembly transverse actuator 144, and may includea housing, a plate, or the like. In the embodiment depicted in FIGS. 3and 4, the recoat assembly 200 further includes at least one tiltactuator 164 that is operable to tilt the base member 250 of the recoatassembly 200 (e.g., about an axis extending in the X-direction asdepicted in FIG. 4). As described in greater detail herein, inembodiments, the tilt actuator 164 may tilt the base member 250 of therecoat assembly 200. In embodiments, the tilt actuator 164 may also tiltthe base member 250 to provide access to an underside of the recoatassembly 200 such that maintenance may be performed on the recoatassembly 200.

Referring to FIGS. 3 and 5, in some embodiments, the recoat assembly 200further includes a base member rotational actuator 162 coupled to thebase member 250. The base member rotational actuator 162 is operable torotate the base member 250 about an axis extending in the verticaldirection (e.g., in the Z-direction as depicted). In embodiments, thebase member rotational actuator 162 and the tilt actuator 164 mayinclude any suitable actuators, for example and without limitation, aworm drive actuator, a ball screw actuator, a pneumatic piston, ahydraulic piston, an electro-mechanical linear actuator, or the like.

In some embodiments and referring to FIGS. 4 and 6A, the recoat assembly200 may include a tilt locking member 161 that is selectively engagablewith the base member 250. For example, the tilt locking member 161 mayselectively restrict movement of the base member 250 about the X-axisshown in FIG. 4. By selectively restricting movement of the base member250, the orientation of the base member 250 can be maintained withoutthe application of force by the tilt actuator 164. In this way, the basemember 250 can be maintained in a tilted position as shown in FIG. 4while maintenance is performed on the recoat assembly 200 withoutrequiring the application of energy to the tilt actuator 164. In someembodiments, the recoat assembly 200 further includes a first rotationallocking member 163 and/or a second rotational locking member 165. Thefirst rotational locking member 163 and/or the second rotational lockingmember 165 may selectively restrict movement of the base member 250about the Z-axis depicted in FIG. 4. In embodiments, the recoat assembly200 includes a powder spreading member, such as one or more rollers,that distribute build material 31 (FIG. 2A).

For example and referring to FIG. 6B and 6C, a side view of the recoatassembly 200 and a view of rollers 202, 204 of the recoat assembly 200are depicted, respectively. In embodiments, the recoat assembly 200includes a first roller support 210, a second roller support 212, and afirst roller 202 disposed between and supported by the first rollersupport 210 and the second roller support 212. In the embodimentdepicted in FIGS. 6B and 6C, the recoat assembly 200 further includes athird roller support 216, a fourth roller support 218, and a secondroller 204 disposed between and supported by the third roller support216 and the fourth roller support 218. In embodiments, the second roller204 is positioned rearward of the first roller 202 (i.e., in the−X-direction as depicted). In these embodiments, the first roller 202may generally be referred to as the “front” roller, and the secondroller 204 may be referred to as the “rear” roller.

In embodiments, the recoat assembly 200 includes a roller verticalactuator 252 that is coupled to the first roller 202 and/or the secondroller 204. The roller vertical actuator 252 is operable to move thefirst roller 202 and/or the second roller 204 with respect to the basemember 250 in the vertical direction (i.e., in the Z-direction asdepicted). In some embodiments, the vertical actuator 252 is coupled tothe front roller 202 and the rear roller 204 such that the front roller202 and the rear roller 204 are moveable with respect to the base member250 independently of one another. In some embodiments, the rollervertical actuator 252 is a first roller vertical actuator 252 coupled tothe first roller 202, and the recoat assembly 200 further includes asecond roller vertical actuator 254 coupled to the second roller 204,such that the front roller 202 and the rear roller 204 are moveable withrespect to the base member 250 independently of one another. The firstand second roller vertical actuators 252, 254 may include any suitableactuators, for example and without limitation, pneumatic actuators,motors, hydraulic actuators, or the like.

The recoat assembly 200 further includes a first rotational actuator 206coupled to the first roller 202 as best shown in FIG. 11B. In someembodiments, the first rotational actuator 206 is spaced apart from thefirst roller 202, and may be coupled to the first roller 202 through abelt, a chain, or the like. In embodiments in which the recoat assembly200 includes the second roller 204, the recoat assembly 200 may includea second rotational actuator 208, best shown in FIG. 11B, coupled to thesecond roller 204. In some embodiments, the second rotational actuator208 is spaced apart from the second roller 204, and may be coupled tothe second roller 204 through a belt, a chain, or the like. In someembodiments, the recoat assembly 200 may include a single rotationalactuator coupled to both the first roller 202 and the second roller 204.In some embodiments, the first rotational actuator 206 is directlycoupled to the first roller 202 and/or the second rotational actuator208 is directly coupled to the second roller 204.

The first rotational actuator 206 is configured to rotate the rotate thefirst roller 202 about a first rotation axis 226. Similarly, the secondrotational actuator 208 is configured to rotate the second roller 204about a second rotation axis 228. In the embodiment depicted in FIG. 6C,the first rotation axis 226 and the second rotation axis 228 aregenerally parallel to one another and are spaced apart from one anotherin the X-direction as depicted. As described in greater detail herein,the first roller 202 and the second roller 204 may be rotated in a“rotation direction” (e.g., a clockwise direction from the perspectiveshown in FIG. 6C) and/or a “counter-rotation direction” that is theopposite of the rotation direction (e.g., a counter-clockwise directionfrom the perspective shown in FIG. 6C). The first and second roller 202,204 can be rotated in the same direction or may be rotated in oppositedirections from one another. The first and second rotational actuators206, 208 may include any suitable actuator for inducing rotation of thefirst and second rollers 202, 204, such as and without limitation,alternating current (AC) or direct current (DC) brushless motors, linearmotors, servo motors, stepper motors, pneumatic actuators, hydraulicactuators, or the like.

In embodiments, the recoat assembly 200 includes one or more sensorsmechanically coupled to the roller supports 210, 212, 216, and/or 218,the one or more sensors configured to output a signal indicative offorces incident on the roller supports 210, 212, 216, and/or 218 via thefirst roller 202 and/or the second roller 204.

For example and referring to FIGS. 7A-7C, in embodiments, a strain gauge240A is mechanically coupled to the first roller support 210. In someembodiments, the strain gauge 240A is a first strain gauge 240A, and asecond strain gauge 240B is mechanically coupled to the first rollersupport 210. While reference is made herein to the strain gauges 240A,240B being mechanically coupled to the first roller support 210, itshould be understood that one or more strain gauges may be coupled toany or all of the first, second, third, and fourth roller supports 210,212, 216, 218.

In embodiments, the roller supports 210, 212, 216, and/or 218 define oneor more flexures 214 to which the strain gauges 240A, 240B are coupled.The strain gauges 240A, 240B are configured to detect elasticdeformation of the flexures 214, which may generally correlate to forcesacting on the roller supports 210, 212, 216, and/or 218. In the depictedembodiment, the flexures 214 are walls of a cavity extending through theroller supports 210, 212, 216, and/or 218, however, it should beunderstood that the flexures 214 may include any suitable portion of theroller supports 210, 212, 216, and/or 218 that elastically deform suchthat strain of the flexures 214 may be determined.

In embodiments, the strain gauges 240A, 240B are oriented in order tomeasure a strain. For example, in the embodiment depicted in FIGS. 7Aand 7B, the strain gauges 240A, 240B are oriented in the verticaldirection (i.e., in the Z-direction as depicted and transverse to thefirst rotation axis 226), and measure a strain in a resultant vector atsome angle between the horizontal (X-axis) and the vertical (Z-axis)direction. By measuring strain in the resultant vector direction, normalforces, i.e., forces acting on the roller supports 210, 212, 216, and/or218 in a direction transverse to a coating direction, can be determined.For example, forces normal to the X-direction and Z-direction may beimparted on the roller supports 210, 212, 216, and/or 218 by buildmaterial 31 (FIG. 2A) distributed by the recoat assembly 200, and/or bycured binder 50 (FIG. 2A), as the recoat assembly 200 moves buildmaterial 31 over build area 124 to cover the build material 31 (FIG. 2)and/or cured binder 50 with a layer of build material 31. One or moreparameters of the operation of the recoat assembly 200 may be changed toreduce normal forces acting on the roller supports 210, 212, 216, and/or218 to maintain the structural integrity of build material 31 bound bythe cured binder 50 (FIG. 2C) positioned beneath build material 31, asdescribed in greater detail herein.

Referring to FIG. 8, in some embodiments, one or both of the straingauges 240A, 240B are oriented in a horizontal direction (i.e., in theX-direction as depicted and transverse to the first rotation axis 226),and may measure a strain in a resultant vector at some angle between thehorizontal (X-axis) and the vertical (Z-axis) direction. In someembodiments, the strain gauges 240A, 240B may be oriented in thehorizontal direction on the first and second roller supports 210, 212,while the strain gauges 240A, 240B may be oriented in the verticaldirection, as depicted in FIGS. 7A-7B, on the third and fourth rollersupports 216, 218. By measuring strain in the horizontal direction(i.e., in the X-direction as depicted), shear forces, i.e., forcesacting on the roller supports 210, 212, 216, and/or 218 in a directioncorresponding to a coating direction, can be determined. For example,shear forces may be imparted on the roller supports 210, 212, 216,and/or 218 by build material 31 (FIG. 2A) distributed by the recoatassembly 200, and/or by build material 31 bound by cured binder 50 (FIG.2A) as the recoat assembly 200 moves to the build area 124 to cover aprevious layer the build material 31 bound by cured binder 50 and/or thebuild material 31 with another layer of build material 31. One or moreparameters of the operation of the recoat assembly 200 may be changed toreduce shear forces acting on the roller supports 210, 212, 216, and/or218 to maintain the structural integrity of the build material 31 boundby cured binder 50 (FIG. 2A), as described in greater detail herein. Asdescribed in greater detail herein, determined forces can also beutilized in open-loop (i.e., feedforward) control of the recoat assembly200 and/or closed-loop (i.e., feedback) control of the recoat assembly200. For example, in embodiments, determined forces may be compared to alookup table of desired forces, and one or more parameters of theoperation of the recoat assembly 200 may be changed based on thecomparison of the determined forces as compared to the desired forces.In embodiments, the forces acting on the roller supports 210, 212, 216,and/or 218 may depend on any of a number of factors, including but notlimited to, a layer thickness of the build material 31 (FIG. 2A), atraverse speed of the recoat assembly 200 (FIG. 2A), the direction androtational speed of the first and/or second roller 202, 204 (FIG. 6C),on the type/composition of build material 31 (FIG. 2A), the particlesize of the build material 31 (FIG. 2A), the type/composition of thebinder 50 (FIG. 2A), the volume (or saturation) of binder material 50(FIG. 2A), on if and how the binder is partially or fully cured in situ,on the geometry of the component being built, etc.

In some embodiments, information related to a current layer of theobject being built and/or a prior layer may be utilized to generate anexpected force or pressure curve to be experienced as the recoatassembly 200 traverses the build area 124. In some embodiments, ageometry of the current layer of the object being built or a geometry ofthe immediately preceding layer that was built may be used to determinean expected pressure or force profile (e.g., shear forces expected to beexperienced as the recoat assembly 200 traverses the build area 124 todistribute material for the current layer, normal forces expected to beexperienced as the recoat assembly 200 traverses the build area 124 todistribute material for the current layer and/or any other type ofexpected force to be experienced as the recoat assembly 200 traversesthe build area 124 to distribute material for the current layer), outputsignals from the one or more sensors coupled to the roller supports(e.g., one or more strain gauges and/or one or more load cells) may beused to calculate a measured force or pressure as the recoat assembly200 traverses the build area 124 to distribute material for the currentlayer, a comparison between the expected pressure or measured forceprofile and the measured force or pressure may be made, and an actionmay be taken in response to the comparison. In some embodiments, alookup table containing expected force or pressure information may bepreviously generated, such as based on calibration force measurementsgenerated under various conditions (e.g., size of build area coated withbinder, recoat traverse speed, recoat roller rotation speed, layerthickness, recoat roller geometry coating, and the like). For example,in some embodiments, when an expected pressure or force deviates from ameasured pressure or force during spreading of material for a currentlayer by the recoat assembly 200, the printing recoat process may bedetermined to be defective. The extent of force deviation may be used todetermine a type of defect (e.g., a powder defect, a recoat rollerdefect, insufficient binder cure, a jetting defect, or the like). When adeviation beyond a given threshold is determined to have occurred, acorrective action may be taken, such as to adjust a recoat traversespeed for the current layer, adjust a roller rotation speed for thecurrent layer, adjust a recoat traverse speed for one or more subsequentlayers, adjust a roller rotation speed for one or more subsequentlayers, adjust a height of one or more rollers for the current layerand/or for one or more subsequent layers, etc. Such measurements,comparisons, and control actions may be implemented by the electroniccontrol unit 300 executing one or more instructions stored in its memorycomponent.

In some embodiments, the one or more sensors mechanically coupled to theroller supports 210, 212, 216, and/or 218 may include a load cell.

For example and referring to FIGS. 9A-9D, in embodiments a load cell 242is mechanically coupled to the first roller support 210, and isconfigured to measure a force in the vertical direction (i.e., in theZ-direction as depicted and transverse to the first rotation axis 226).As shown in FIG. 9C, in some embodiments, a set screw 246 may engage theload cell 242 to calibrate the load cell 242, for example, by applying aknown amount of force to the load cell 242.

Referring to FIG. 10, in some embodiments, the first roller support 210may include both the load cell 242 and the strain gauges 240A, 240B.While in the embodiment depicted in FIG. 10, the strain gauges 240A,240B are oriented in the horizontal direction, it should be understoodthat one or both of the strain gauges 240A, 240B may be oriented in thevertical direction.

In some embodiments, an accelerometer 244 is coupled to the first rollersupport 210. While in the embodiment depicted in FIG. 10, the load cell242, the strain gauges 240A, 240B, and the accelerometer 244 are coupledto the first roller support 210, it should be understood that in someembodiments, only the accelerometer 244 may be mechanically coupled tothe first roller support 210. In some embodiments, the accelerometer 244is coupled to the first roller support 210 along with any combination ofthe load cell 242, the strain gauge 240A, and/or the strain gauge 240B.Furthermore, the accelerometer 244 may be coupled to any of the rollersupports 210, 212, 216, and/or 218.

In some embodiments, a roller support temperature sensor 247 is coupledto the first roller support 210. The roller support temperature sensor247 is operable to detect a temperature of the roller support 210, whichmay be utilized to calibrate and/or compensate for a load cell readingfrom the load cell 242. While in the embodiment depicted in FIG. 10, theload cell 242, the strain gauges 240A, 240B, the accelerometer 244, andthe roller support temperature sensor 247 are coupled to the firstroller support 210, it should be understood that in some embodiments,only the roller support temperature sensor 247 may be mechanicallycoupled to the first roller support 210. In some embodiments, the rollersupport temperature sensor 247 is coupled to the first roller support210 along with any combination of the load cell 242, the strain gauge240A, the strain gauge 240B, and/or the accelerometer 244. Furthermore,the roller support temperature sensor 247 may be coupled to any of theroller supports 210, 212, 216, and/or 218.

Referring to FIG. 11A, in some embodiments, the recoat assembly 200generally includes a front energy source 260 coupled to the base member250 and positioned forward of the front roller 202 (i.e., in the+X-direction as depicted). The recoat assembly 200, in the embodimentdepicted in FIG. 11A, further includes a rear energy source 262 coupledto the base member 250 and positioned rearward of the rear roller 204(i.e., in the −X-direction as depicted). The front energy source 260generally emits energy forward of the front roller 202, and the rearenergy source 262 emits energy rearward of the rear roller 204. Inembodiments, the front and rear energy sources 260, 262 may generallyemit electromagnetic radiation, such as infrared radiation, ultravioletradiation, or the like. In some embodiments, the front and rear energysources 260, 262 may emit energy, which may act to heat build material31 (FIG. 2A) and/or cure binder material 50 (FIG. 2A) on the buildmaterial 31, as described in greater detail herein. While in theembodiment depicted in FIG. 11A, the front energy source 260 ispositioned forward of the front roller 202 and the rear energy source262 is positioned rearward of the rear roller 204, it should beunderstood that this is merely an example. For example in someembodiments, the front energy source 260 and the rear energy source 262may both be positioned forward of the front roller 202, as shown in FIG.6A, or the front energy source 260 and the rear energy source 262 mayboth be positioned rearward of the front roller 202 and the rear roller204. By including multiple energy sources (e.g., the front energy source260 and the rear energy source 262), energy can be applied to buildmaterial 31 (FIG. 1A) over a comparatively longer period of time ascompared to the application of energy via a single energy source. Inthis way, over-cure of build material 31 bound by cured binder 50 can beminimized. While in the embodiment depicted in FIG. 11A, a front energysource 262 and a rear energy source 262 are depicted, it should beunderstood that embodiments described herein can include any suitablenumber of energy sources positioned in any suitable manner forward andrearward of the front roller 202 and the rear roller 204. Referring toFIGS. 11B-11D, in some embodiments, the recoat assembly 200 includes oneor more hard stops 410 coupled to the base member 250. While a singlehard stop 410 is shown in the section views depicted in FIGS. 11C and11D, it should be understood that each of the hard stops 410 may beidentical. Moreover, although in the embodiment depicted in FIG. 11B therecoat assembly 200 includes two hard stops 410, it should be understoodthat the recoat assembly 200 may include a single hard stop 410 or anysuitable number of hard stops 410.

The hard stops 410 may assist in limiting movement of the first roller202 and/or the second roller 204 about the Y-axis as depicted, forexample, as a result of actuation of the roller vertical actuator 252.For example and referring particularly to FIGS. 11A, 11C, and 21, insome embodiments, the roller vertical actuator 252 is coupled to apivoting portion 249 of the base member 250 that is movable with respectto a stationary portion 251 of the base member 250 about the Y-axis asdepicted. The first roller 202 and the second roller 204 may be coupledto the pivoting portion 249, such that movement of the pivoting portion249 about the Y-axis results in movement of the first roller 202 and/orthe second roller 204 about the Y-axis as depicted.

In embodiments, the hard stop 410 includes a coupling portion 414 thatis coupled to the pivoting portion 249 of the base member 250, and apost portion 412 that is movably engaged with the stationary portion 251of the base member 250. For example, the post portion 412 of the hardstop 410 may be movable with respect to the stationary portion 251 in avertical direction (e.g., in the Z-direction as depicted). Movement ofthe post portion 412 of the hard stop 410 in the vertical direction(e.g., in the Z-direction as depicted) may be restricted. For example, anut 420 may be adjustably engaged with the post portion 412, and mayrestrict movement of the post portion 412 with respect to the stationaryportion 251 of the base member 250. Because the coupling portion 414 ofthe hard stop 410 is coupled to the pivoting portion 249 of the basemember 250, restriction of the movement of the post portion 412 of thehard stop 410 with respect to the stationary portion 251 therebyrestricts movement of the pivoting portion 249 with respect to thestationary portion 251 in the vertical direction (e.g., in theZ-direction as depicted). In some embodiments, the nut 420 is adjustableon the post portion 412 in the Z-direction as depicted. By moving thenut 420 along the post portion 412 in the Z-direction, the freedom ofmovement of the pivoting portion 249 of the base member 250, andaccordingly the first roller 202 and/or the second roller 204, withrespect to the stationary portion 251 of the base member 250 can beadjusted. Through the hard stop 410, movement of the pivoting portion249 of the base member 250, and accordingly the first roller 202 and/orthe second roller 204, via actuation of the roller vertical actuator 250can be precisely tuned as desired. While in the embodiment depicted inFIGS. 11C and 11D the hard stop 410 includes the nut 420 that limitsmovement of the hard stop 410, it should be understood that this ismerely an example. For example, in some embodiments, the movement of thehard stop 410 may be limited by a manual micrometer, one or more motors,or the like. For example and as best shown in FIG. 16B, in someembodiments, the recoat assembly may include multiple hard stops 410that limit movement of the first roller 202 and the second roller aboutthe Y-axis as depicted. The hard stops 410 may include micrometers formoving a position of the hard stops 410. In some embodiments, the hardstops 410 may further include a load cell for detecting a position ofthe hard stop 410.

In some embodiments, the post portion 412 of the hard stop 410 extendsthrough an aperture 253 extending through the stationary portion 251 ofthe base member 250. In some embodiments, the recoat assembly 200includes a dust shield 430 that at least partially encapsulates theaperture 253 and/or at least a portion of the hard stop 410. For examplein the embodiment depicted in FIGS. 11C and 11D, the dust shield 430includes an upper portion 432 that at least partially covers an upperopening of the aperture 253 and the post portion 414 of the hard stop410, and a lower portion 434 that at least partially covers a loweropening of the aperture 253. The dust shield 430 may further include alower biasing member 436 that biases the lower portion 434 of the dustshield 430 into engagement with the aperture 253. The dust shield 430may further include an upper biasing member 438 that biases the upperportion 432 of the dust shield 430 into engagement with the aperture253. By at least partially enclosing the aperture 253, the dust shield430 may assist in preventing build material 31 (FIG. 1) from enteringthe aperture 253 and interfering with movement of the post portion 412of the hard stop 410 through the aperture 253. Further, in embodiments,the lower biasing member 436 and/or the upper biasing member 438 may atleast partially offset tension resulting from a connection between thefirst rotational actuator 206 and the first roller 202 and/or betweenthe second rotational actuator 208 and the second roller 204. Forexample, as shown in FIG. 11B, the first rotational actuator 206 may becoupled to the first roller 202 via a belt. Similarly, the secondrotational actuator 208 may be coupled to the second roller 204 via abelt. Tension in the belts may cause movement of the first roller 202and/or the second roller 204 in the Z-direction as depcited. Thismovement may be opposed by the lower biasing member 436 and/or the upperbiasing member 438, thereby stabilizing the position of the first roller202 and/or the second roller 204 in the Z-direction as depicted.

Referring to FIG. 11E, a lower perspective view of the recoat assembly200 is schematically depicted. In some embodiments, the recoat assembly200 includes a powder guide 450 pivotally coupled to the base member 250of the recoat assembly 200 at a pivot point 452. The powder guide 450may be pivotable with respect to the base member 250 about the Y-axis asdepicted. By pivoting with respect to the base member 250 about theY-axis, the powder guide 450 may maintain contact with the buildplatform 20 (FIG. 1) and/or the supply platform 30 (FIG. 1) as therollers 202, 204 move in the Z-direction as depicted. The powder guide450 may assist in restricting the flow of build material 31 (FIG. 1) inthe Y-direction away from recoat assembly 200.

Referring to FIGS. 11A and 12, in some embodiments, the front energysource 260 and the rear energy source 262 are each positioned at leastpartially within an energy source housing 264. The energy sourcehousings 264 can, in some embodiments, focus energy emitted by the frontenergy source 260 and the rear energy source 262, and may include areflective interior surface or the like.

In some embodiments, the recoat assembly 200 includes one or morehousing temperature sensors 266. In the embodiment depicted in FIG. 12,the recoat assembly 200 includes a housing temperature sensor 266coupled to the energy source housing 264 of the front energy source 260,and a housing temperature sensor 266 coupled to the energy sourcehousing 264 of the front energy source 262. In embodiments, the housingtemperature sensors 266 are configured to detect a temperature of therespective front and rear energy sources 260, 262 and/or the energysource housings 264. The energy emitted by the front and rear energysources 260, 262 may be controlled based at least in part on thedetected temperature of the front and rear energy sources 260, 262and/or the energy source housings 264, so as to prevent damage to thefront and rear energy sources 260, 262 and/or the energy source housings264 and/or to ensure that appropriate energy is applied to the buildmaterial 31.

In some embodiments, the recoat assembly 200 includes one or morehousing engagement members 257 positioned at outboard ends of the recoatassembly 200 and engaged with a housing of the additive manufacturingsystem 100. The housing engagement members 257 are generally configuredto engage and “plow” or “scrape” build material 31 off of the sides ofthe additive manufacturing system 100. In embodiments, the housingengagement members 257 may include any structure suitable, such asbrushes, blades, or the like.

Referring to FIG. 12, a side view of the recoat assembly 200 isschematically depicted. In embodiments, the front roller 202 has a frontroller diameter d1, and the rear roller 204 has a rear roller diameterd2. In some embodiments, the front roller diameter d1 is different fromthe rear roller diameter d2 For example, in some embodiments, the frontroller diameter d1 is less than the rear roller diameter d2. Inembodiments, the front roller diameter d1 is between 20 millimeters and25 millimeters, inclusive of the endpoints. In some embodiments, thefront roller diameter d1 is between 10 millimeters and 40 millimeters,inclusive of the endpoints. In some embodiments, the front rollerdiameter d1 is less than about 22.23 millimeters. As described ingreater detail herein, a relatively small diameter may assist the frontroller 202 in fluidizing build material 31 to distribute the buildmaterial 31. In embodiments, the rear roller diameter d2 is between 35millimeters and 40 millimeters, inclusive of the endpoints. Inembodiments, the rear roller diameter d2 is between 20 millimeters and60 millimeters, inclusive of the endpoints. In some embodiments, therear roller diameter d2 is greater than about 38.1 millimeters. Asdescribed in greater detail herein, a relatively large diameter mayassist the rear roller 204 in compacting build material 31.

In some embodiments, the recoat assembly 200 includes a powder engagingmember 255 coupled to the base member 250 (FIG. 11A) and positionedforward of the front roller 202. In embodiments, the powder engagingmember 255 is positioned at a height evaluated in the vertical direction(i.e., in the Z-direction as depicted) that is within a roller window Rwdefined by the front roller 202. The powder engaging member 255 may be a“doctor” blade that generally acts to plow and clear build material 31forward of the front roller 202, thereby minimizing a height of buildmaterial 31 contacted by the front roller 202. While in the depictedembodiment, the recoat assembly 200 includes the powder engaging member255 and the front and rear rollers 202, 204, it should be understoodthat in some embodiments, the recoat assembly 200 may include only thepowder engaging member 255 to spread build material 31. While in theembodiment depicted in FIG. 12, the powder engaging member 255 ispositioned forward of the front roller 202, embodiments described hereinmay include a single or multiple powder engaging members positionedforward of the front roller 202 and/or rearward of the rear roller 204.

In some embodiments, the recoat assembly 200 includes multiple frontrollers 202 and/or multiple rear rollers 204.

For example and referring to FIG. 13, a top view of one configuration offront rollers 202A, 202B and rear rollers 204A, 204B is schematicallydepicted. In the embodiment depicted in FIG. 13, the recoat assembly 200includes a first front roller 202A and a second front roller 202B thatis spaced apart from the first front roller 202A in the lateraldirection (i.e., in the Y-direction as depicted). In the embodimentdepicted in FIG. 13, the recoat assembly 200 further includes a firstrear roller 204A and a second rear roller 204B spaced apart from thefirst rear roller 204A in the lateral direction (i.e., in theY-direction as depicted). While the embodiment depicted in FIG. 13includes the two front rollers 202A, 202B and two rear rollers 204A,204B, it should be understood that the recoat assembly 200 may includeany suitable number of front rollers spaced apart from one another inthe lateral direction (i.e., in the Y-direction as depicted), and anysuitable number of rear rollers spaced apart from one another in thelateral direction. In some embodiments, the recoat assembly 200 mayinclude the two front rollers 202A, 202B, and a single rear roller, orthe two rear rollers 204A, 204B with a single front roller. By includingmultiple front rollers 202A, 202B, aligned with one another in thelateral direction (i.e., in the Y-direction as depicted), and/or byincluding multiple rear rollers 204A, 204B aligned with one another inthe lateral direction, the recoat assembly 200 may extend a greaterdistance in the lateral direction, as compared to recoat assembliesincluding a single front roller and a single rear roller. As an exampleand without being bound by theory, the longer a roller extends in thelateral direction (i.e., in the Y-direction as depicted), the moresusceptible the roller may be to elastic and/or inelastic deformationdue to forces acting on the roller. Accordingly, the width of recoatassemblies including a single front roller and a single rear roller maybe effectively limited, which may limit the size of objects that may bebuilt by the additive manufacturing system 100. However, by includingmultiple front rollers 202A, 202B, aligned with one another in thelateral direction (i.e., in the Y-direction as depicted), and/or byincluding multiple rear rollers 204A, 204B aligned with one another inthe lateral direction, the recoat assembly 200 may extend a greaterdistance in the lateral direction.

Referring to FIG. 14, in some embodiments, the front rollers 202A, 202Boverlap one another in the lateral direction (i.e., in the Y-directionas depicted). In embodiments in which the recoat assembly 200 includesthe two rear rollers 204A, 204B, the two rear rollers may similarlyoverlap one another in the lateral direction (i.e., in the Y-directionas depicted). By overlapping the front rollers 202A, 202B and/or therear rollers 204A, 204B in the lateral direction (i.e., in theY-direction as depicted), the front rollers 202A, 202B and/or the rearrollers 204A, 204B may prevent build material 31 (FIG. 12) from passingbetween adjacent front rollers 202A, 202B and/or adjacent rear rollers204A, 204B.

Referring to FIG. 15, in some embodiments, rollers are positioned toextend across gaps defined by adjacent rollers. For example, in theembodiment depicted in FIG. 15, the recoat assembly 200 includes threefront rollers 202A, 202B, and 202C, wherein adjacent front rollers 202A,202B define a gap G1 positioned between the rollers 202A, 202B in thelateral direction (i.e., in the Y-direction as depicted), and adjacentfront rollers 202B, 202C define a gap G2 positioned between the rollers202B, 202C in the lateral direction. The recoat assembly 200 includes arear roller 204A extending between the adjacent front rollers 202A,202B, and rear roller 204B extending between the adjacent front rollers202B, 202C. In particular, the rear roller 204A extends across the gapG1 between the adjacent front rollers 202A, 202B, and the rear roller204B extends across the gap G2 between the adjacent front rollers 202B,202C. By extending across the gaps G1, G2, the rear rollers 204A, 204Bmay engage build material 31 (FIG. 12) that passes through the gaps G1,G2.

Referring to FIG. 16A, in some embodiments, the recoat assembly 200includes a cleaning member 270. In embodiments, the cleaning member 270that is selectively engagable with at least one roller. For example, inthe embodiment depicted in FIG. 16A, the cleaning member 270 ispositioned between and engaged with the first roller 202 and the secondroller 204. In the embodiment depicted in FIG. 16A, the cleaning member270 generally engages both the first roller 202 and the second roller204 along the length of the first roller 202 and the second roller 204evaluated in the lateral direction (i.e., in the Y-direction asdepicted) and generally removes build material 31 (FIG. 12) and/or curedbinder 50 (FIG. 12) that may remain attached to the first roller 202 andthe second roller 204 as the first roller 202 and the second roller 204rotate. In some embodiments, the cleaning member 270 is a cleaningroller including grooves 272 or brush that is configured to rotate whileengaged with the first roller 202 and the second roller 204. In someembodiments, the cleaning member 270 may include a blade or the likethat removes build material 31 (FIG. 12) from the first roller 202 andthe second roller 204. While in the embodiment depicted in FIG. 16A thecleaning member 270 is simultaneously engaged with the first roller 202and the second roller 204, it should be understood that the cleaningmember 270 may in some embodiments be engaged solely with either thefirst roller 202 or the second roller 204. Moreover, while theembodiment depicted in FIG. 16A depicts a single cleaning member 270, itshould be understood that in embodiments, the recoat assembly 200 mayinclude multiple cleaning members 270.

In some embodiments, the position of the cleaning member 270 can beadjusted with respect to the first roller 202 and/or the second roller204. For example and referring to FIGS. 16B, 16C, and 16D, in someembodiments, the recoat assembly 200 includes a cleaning positionadjustment assembly 500. In some embodiments, the cleaning positionadjustment assembly 500 includes a first rotational member 510 and asecond rotational member 520. As best shown in FIG. 16D, in someembodiments, the first rotational member 510 includes a first notchedflange 512 and a first eccentric tube 514. The second rotational member520 includes a second notched flange 522 and a second eccentric tube524. In embodiments, the first eccentric tube 514 is insertable withinthe second eccentric tube 524, as shown in FIG. 16C. The cleaningposition adjustment assembly 500 may further include a bearing 530 thatis insertable within the first eccentric tube 514, and the cleaningmember 270 is engaged with the bearing 530.

By rotating the first rotational member 510 and/or the second rotationalmember 520 with respect to one another, the position of the cleaningmember 270 with respect to the base member 250, and accordingly thefirst roller 202 and the second roller 204, may be adjusted. Forexample, the position of the second rotational member 520 with respectto the base member 250 may be generally fixed. As the first rotationalmember 510 and the second rotational member 520 rotate with respect toone another, the eccentricity of the first eccentric tube 514 and thesecond eccentric tube 524 move the cleaning member 270 with respect tothe base member 250, and accordingly with respect to the first roller202 and the second roller 204. In this way, a user, such as atechnician, can adjust the position of the cleaning member 270 withrespect to the first roller 202 and the second roller 204. In someembodiments, the cleaning position adjustment assembly 500 furtherincludes one or more pins 540 that are insertable into the base member250 through notches of the first notched flange 512 and the secondnotched flange 522. The one or more pins 540 restrict rotationalmovement of the first rotational member 510 and the second rotationalmember 520 with respect to one another, and with respect to the basemember 250. The one or more pins 540 may be positioned into the basemember 250 through notches of the first notched flange 512 and thesecond notched flange 522, for example by a technician, once thecleaning member 270 is positioned as desired. In some embodiments, thefirst rotational member 510 and/or the second rotational member 520 maybe rotated with respect to one another and/or retained in position by anactuator or the like.

Referring to FIGS. 17A-17C, top views and a side view of the cleaningmember 270 engaged with the first and second rollers 202, 204 areschematically depicted. As shown in FIG. 17A, in some embodiments, suchas embodiments in which the first roller 202 and the second roller 204are offset from one another in the lateral direction (i.e., in theY-direction as depicted), the cleaning member 270 may extend along thelength of both the first roller 202 and the second roller 204 in thelateral direction. As shown in FIG. 17B, the cleaning member 270 maysimilarly extend along the length of both the first roller 202 and thesecond roller 204 in the lateral direction (i.e., in the Y-direction asdepicted) in embodiments in which the first roller 202 and the secondroller 204 are aligned with one another. In embodiments, as depicted inFIG. 17C, the cleaning member 270 is generally positioned above thefirst roller 202 and the second roller 204 in the vertical direction(i.e., in the Z-direction as depicted).

Referring to FIGS. 11A, 18A, 18B, and 22 in some embodiments, the recoatassembly 200 is in fluid communication with a vacuum 290. In particular,in embodiments, the vacuum 290 is in fluid communication with at least aportion of the base member 250 of the recoat assembly 200. The vacuum290 is generally operable to draw airborne build material 31 (FIG. 12)out of the recoat assembly 200 and/or control the flow of aerosolizedbuild material 31 within the additive manufacturing system 100 (FIG.2A). In particular, as the rollers 202, 204 (FIG. 19) fluidize buildmaterial 31 (FIG. 17C), some build material 31 will become airborne,unless controlled, may foul components of the additive manufacturingsystem 100. The vacuum 290, in embodiments, may include any suitabledevice for applying a negative and/or a positive pressure to the recoatassembly 200, such as a pump or the like. As depicted in FIG. 18A, thebase member 250 generally includes a secondary containment housing 278.In some embodiments, the primary containment housing 276 and/or thesecondary containment housing 278 may include one or more adjustableopenings 279 that can be adjustably opened and closed to selectivelyrestrict the flow of air and/or build material through the primarycontainment housing 276 and/or the secondary containment housing 278.For example and as shown in FIGS. 11A and 23, the primary containmenthousing includes a first adjustable opening 279 and a second adjustableopening 279′. The recoat assembly 200 may further include a firstmovable cover 269 that can selectively cover the first adjustableopening 279. For example, the first moveable cover 269 may be movable inthe Z-direction as depicted to selectively widen or narrow the firstadjustable opening 279 (evaluated in the Z-direction as depicted).Similarly, the recoat assembly 200 may include a second movable cover269′ that can selectively cover the second adjustable opening 279′. Forexample, the second moveable cover 269′ may be movable in theZ-direction as depicted to selectively widen or narrow the secondadjustable opening 279′ (evaluated in the Z-direction as depicted)independently of the first adjustable opening 279. By widening ornarrowing the first and/or second adjustable openings 279, 279′, airflowinto the primary containment housing 276 can be tuned as desired todirect flow of airborne build material 31. FIG. 18B shows the basemember 250 with the secondary containment housing 278 removed, anddepicts a primary containment housing 276 of the base member 250.

Without being bound by theory, airborne build material 31 may includeparticles that are smaller than the average particle size of the buildmaterial 31 that does not become airborne. Accordingly, by drawingairborne build material 31 of smaller size out of the recoat assembly200, the mean particle size of the build material 31 in the supplyreceptacle 134 (FIG. 2A) and/or the build area 124 (FIGS. 2A, 2B) mayincrease. Accordingly, in some embodiments, build material 31 includingsmaller particles, such as the build material 31 drawn from the recoatassembly 200, may be periodically re-introduced to the supply receptacle134 (FIG. 2A) and/or the build material hopper 360 (FIG. 2A) to maintaina relatively consistent particle size of the build material 31.

Referring to FIG. 19, a section view of the base member 250 is depicted.In embodiments, the primary containment housing 276 at least partiallyencapsulates the powder spreading member (e.g., the first and secondrollers 202, 204 and/or the powder engaging member 255 (FIG. 12)). Thesecondary containment housing 278 is spaced apart from the primarycontainment housing 276 and at least partially encapsulates the primarycontainment housing 276. The primary containment housing 276 and thesecondary containment housing 278 generally define an intermediatecavity 277 that is disposed between the primary containment housing 276and the secondary containment housing 278 In embodiments, the vacuum 290is in fluid communication with the intermediate cavity 277, and isoperable to draw airborne build material 31 from the intermediate cavity277. In some embodiments, the intermediate cavity 277 is a forwardintermediate cavity 277, and the secondary containment housing 278 andthe primary containment housing 276 define a rear intermediate cavity283 separated from the forward intermediate cavity 277 by a bulkhead281. By separating the forward intermediate cavity 277 and the rearintermediate cavity 283, different vacuum pressures may be applied tothe forward intermediate cavity 277 and the rear intermediate cavity283. For example, the rear intermediate cavity 283 may pass overgenerally settled build material 31, and accordingly, it may bedesirable to apply less vacuum pressure at the rear intermediate cavity283 to avoid disturbing the settled build material 31.

In some embodiments, the recoat assembly 200 further includes anagitation device 284 coupled to the base member 250. The agitationdevice 284 is operable to vibrate components of the recoat assembly 200,such as the base member 250, the first roller 202, and/or the secondroller 204 to dislodge build material 31 (FIG. 12) that may be attachedto the base member 250 and/or the first roller 202 and the second roller204. Referring to FIGS. 20 and 21, in some embodiments the base member250 may include only the primary containment housing 276 at leastpartially enclosing the powder spreading member (e.g., the first roller202 and/or the second roller 204). In these embodiments, the vacuum 290is in fluid communication with the primary containment housing 276.

Referring to FIG. 22, a section view of the base member 250 isschematically depicted. As shown in FIG. 22, the vacuum 290 is in fluidcommunication with the primary containment housing 276, and generallyoperates to draw airborne build material 31 (FIG. 12). In someembodiments, the recoat assembly 200 includes a diffuser plate 280positioned between the vacuum 290 and the powder spreading member (e.g.,the first roller 202 and/or the second roller 204). The diffuser plate280 generally includes a plurality of apertures 282 extendingtherethrough. The diffuser plate 280 may generally assist indistributing the negative pressure applied to the primary containmenthousing 276 by the vacuum 290.

Referring to FIG. 23, in some embodiments, the vacuum 290 is operable todraw airborne build material 31 from the recoat assembly 200, and isfurther operable to direct the collected build material 31 beneath therecoat assembly 200 in the vertical direction (i.e., in the Z-directionas depicted). In the embodiment depicted in FIG. 23, the vacuum 290 ispositioned within the primary containment housing 276 and is positionedbetween the first roller 202 and the second roller 204. The vacuum 290generally acts to draw in and collect airborne build material 31 andsubsequently deposit the collected build material 31 below the recoatassembly 200. In the embodiment depicted in FIG. 23, the vacuum 290 ispositioned between the first roller 202 and the second roller 204, andthe vacuum 290 deposits the collected build material 31 between thefirst roller 202 and the second roller 204. In some embodiments, thevacuum 290 may be positioned outside of the recoat assembly 200 and mayredeposit the collected build material 31 at any suitable locationbeneath the recoat assembly 200.

Referring to FIG. 24, a control diagram for the additive manufacturingsystem 100 is schematically depicted. In embodiments, the strain gauges240A, 240B, the load cell 242, and the accelerometer 244 arecommunicatively coupled to an electronic control unit 300. The first andsecond rotational actuators 206, 208, the recoat assembly transverseactuator 144, the recoat assembly vertical actuator 160, and the printhead actuator 154 are communicatively coupled to the electronic controlunit 300, in embodiments. The electronic control unit 300 is alsocommunicatively coupled to the roller vertical actuators 252, 254, thefront and rear energy source 260, 262, the agitation device 284, the oneor more housing temperature sensors 266, and the vacuum 290. In someembodiments, a temperature sensor 286 and a distance sensor 288, and theroller support temperature sensor 247 are also communicatively coupledto the electronic control unit 300 as shown in FIG. 24.

In some embodiments, the electronic control unit 300 includes a currentsensor 306. The current sensor 306 generally senses a current drivingthe recoat assembly transverse actuator 144, the first rotationalactuator 206, the second rotational actuator 208, the vertical actuator160, and/or the print head actuator 154. In embodiments in which therecoat assembly transverse actuator 144, the first rotational actuator206, the second rotational actuator 208, the vertical actuator 160,and/or the print head actuator 154 are electrically actuated, thecurrent sensor 306 senses current driving the recoat assembly transverseactuator 144, the first rotational actuator 206, the second rotationalactuator 208, the vertical actuator 160, and/or the print head actuator154. While in the embodiment depicted in FIG. 24, the current sensor 306is depicted as being a component of the electronic control unit 300, itshould be understood that the current sensor 306 may be a separatecomponent communicatively coupled to the electronic control unit 300.Furthermore, while in the embodiment depicted in FIG. 24, a singlecurrent sensor 306 is depicted, it should be understood that theadditive manufacturing system 100 may include any suitable number ofcurrent sensors 306 associated with the recoat assembly transverseactuator 144, the first rotational actuator 206, the second rotationalactuator 208, the vertical actuator 160, and/or the print head actuator154.

In embodiments, the electronic control unit 300 generally includes aprocessor 302 and a memory component 304. The memory component 304 maybe configured as volatile and/or nonvolatile memory, and as such mayinclude random access memory (including SRAM, DRAM, and/or other typesof RAM), flash memory, secure digital (SD) memory, registers, compactdiscs (CD), digital versatile discs (DVD), bernoulli cartridges, and/orother types of non-transitory computer-readable mediums. The processor302 may include any processing component operable to receive and executeinstructions (such as from the memory component 304). In embodiments,the electronic control unit 300 may store one or more operatingparameters for operating the additive manufacturing system 100, asdescribed in greater detail herein.

Methods for operating the recoat assembly 200 will now be described withreference to the appended drawings.

Referring collectively to FIGS. 24 and 25, an example method ofoperating the recoat assembly 200 is schematically depicted. In a firststep 2502, the electronic control unit 300 receives a first outputsignal of a first sensor. In embodiments, the first sensor ismechanically coupled to and in contact with the first roller support 210(FIG. 6B), and may include any of the first strain gauge 240A, thesecond strain gauge 240B, the load cell 242, and/or the accelerometer244. The first sensor, in embodiments, outputs the first output signal,which is indicative of a first force incident on the first roller 202(FIG. 6B). In a second step 2504, the electronic control unit 300determines the first force on the first roller 202 (FIG. 6B) based onthe first output signal of the first sensor. At step 2506, theelectronic control unit 300 adjusts at least one operating parameter ofthe additive manufacturing system 100 (FIG. 2A) in response to thedetermined first force.

As noted above, in embodiments, the electronic control unit 300 mayinclude one or more parameters for operating the additive manufacturingsystem 100 (FIG. 2A). By adjusting at least one operating parameter inresponse to determined forces acting on the first roller 202 (FIG. 6B),the electronic control unit 300 may actively adjust operation of theadditive manufacturing system 100. As one example, in embodiments, theat least one parameter of the additive manufacturing system 100 (FIG.2A) includes a speed with which the recoat assembly transverse actuator144 moves the recoat assembly 200 (FIG. 2A) relative to the build area124 (FIGS. 2A, 2B). In embodiments, upon determining a force acting onthe first roller 202 below a configurable threshold, the electroniccontrol unit 300 may direct the recoat assembly transverse actuator 144to increase the speed at which the recoat assembly 200 (FIG. 2A) movesrelative to the build area 124 (FIGS. 2A, 2B). For example, thedetermination of comparatively low force or forces acting on the firstroller 202 may be indicative that the speed at which the recoat assembly200 (FIG. 2A) is moved may be increased without detrimentally affectingthe first roller 202. By contrast, upon detecting a force acting on thefirst roller 202 exceeding a configurable threshold, the electroniccontrol unit 300 may direct the recoat assembly transverse actuator 144to decrease the speed at which the recoat assembly 200 (FIG. 2A) movesrelative to the build area 124 (FIGS. 2A, 2B). For example, thedetermination of comparatively high force or forces acting on the firstroller 202 may be indicative that the speed at which the recoat assembly200 (FIG. 2A) should be decreased to reduce the forces acting on thefirst roller 202.

In some embodiments, the at least one parameter is a height of the firstroller 202 (FIG. 6B) evaluated in the vertical direction (e.g., in theZ-direction as depicted in FIG. 6B). In embodiments, upon determining aforce acting on the first roller 202 below a configurable threshold, theelectronic control unit 300 may direct the vertical actuator 160 tolower the recoat assembly 200 relative to the build area 124 (FIGS. 2A,2B). For example, the determination of comparatively low force or forcesacting on the first roller 202 may be indicative that the height atwhich the recoat assembly 200 (FIG. 2A) may be lowered to engage anadditional volume of build material 31 (FIG. 2A). By contrast, upondetecting a force acting on the first roller 202 exceeding aconfigurable threshold, the electronic control unit 300 may direct thevertical actuator 160 to raise the recoat assembly 200 relative to thebuild area 124 (FIGS. 2A, 2B). For example, the determination ofcomparatively high force or forces acting on the first roller 202 may beindicative that the first roller 202 should be raised so as to engage areduced volume of build material 31 (FIG. 2A).

In some embodiments, the at least one parameter of the additivemanufacturing system 100 comprises a speed at which the print headactuator 154 moves the print head 150 (FIG. 2A). In embodiments, upondetermining a force acting on the first roller 202 below a configurablethreshold, the electronic control unit 300 may direct the print headactuator 154 to increase the speed at which the print head actuator 154moves the print head 150 (FIG. 2A) relative to the build area 124 (FIGS.2A, 2B). For example, the determination of comparatively low force orforces acting on the first roller 202 may be indicative that the speedat which first roller 202 (FIG. 2A) moves with respect to the build area124 (FIGS. 2A, 2B) may be increased, and the speed at which the printhead actuator 154 moves the print head 150 may be similarly increased,and/or a volume of binder 50 (FIG. 1A) can be increased. By contrast,upon detecting a force acting on the first roller 202 exceeding aconfigurable threshold, the electronic control unit 300 may direct theprint head actuator 154 to decrease the speed at which the print head150 (FIG. 2A) moves with respect to the build area 124 (FIGS. 2A, 2B).For example, the determination of comparatively high force or forcesacting on the first roller 202 may be indicative that the speed at whichfirst roller 202 (FIG. 2A) moves with respect to the build area 124(FIGS. 2A, 2B) should be decreased, and the speed at which the printhead actuator 154 moves the print head 150 should similarly bedecreased, and/or a volume of binder 50 (FIG. 1A) can be decreased.

In some embodiments, the electronic control unit 300 is configured toadjust the at least one operating parameter of the additivemanufacturing system 100 based on sensed current from the current sensor306. For example, in embodiments, the current sensor 306 may detectcurrent from the first rotational actuator 206 and/or the secondrotational actuator 208. Detection of a current below a configurablethreshold may be generally indicative of relatively low forces acting onthe first roller 202 and/or the second roller 204. By contrast,detection of a current above a configurable threshold may be generallyindicative of relatively high forces acting on the first roller 202and/or the second roller 204. In some embodiments, the current sensor306 may sense a current driving the transverse actuator 144 that movesthe recoat assembly 200 relative to the build area 124. Similar to thefirst and second rotational actuators 206, 208, detection of a currentbelow a configurable threshold may be generally indicative of relativelylow forces acting on the first roller 202 and/or the second roller 204.By contrast, detection of a current above a configurable threshold maybe generally indicative of relatively high forces acting on the firstroller 202 and/or the second roller 204.

Referring to FIGS. 2A, 2B, 24, and 26, another method for adjusting atleast one operating parameter of the additive manufacturing system 100is depicted. In a first step 2602, the method comprises distributing alayer of a build material 31 on the build area with the recoat assembly200. In a second step 2604, the method comprises receiving a firstoutput signal from a first sensor as the layer of the build material 31is distributed on the build area 124 with the recoat assembly 200. Asdescribed above, in embodiments, the first sensor is mechanicallycoupled to and in contact with the first roller support 210 (FIG. 6B),and may include any of the first strain gauge 240A, the load cell 242,and/or the accelerometer 244. The first sensor, in embodiments, outputsthe first output signal, which is indicative of a first force incidenton the first roller 202 (FIG. 6B).

At step 2604, the method comprises determining the first force on thefirst roller 202 based on the first output signal of the first sensor).In some embodiments, a lookup table containing expected force orpressure information may be previously generated, such as based oncalibration force measurements generated under various conditions (e.g.,size of build area coated with binder, recoat traverse speed, recoatroller rotation speed, recoat roller direction, layer thickness, recoatroller geometry coating, and the like). In some embodiments, informationrelated to a current layer of the object being built and/or a priorlayer may be utilized to generate an expected force or pressure curve tobe experienced as the recoat assembly 200 traverses the build area 124.In some embodiments, a geometry of the current layer of the object beingbuilt or a geometry of the immediately preceding layer that was builtmay be used to determine an expected pressure or force profile (e.g.,shear forces expected to be experienced as the recoat assembly 200traverses the build area 124 to distribute material for the currentlayer, normal forces expected to be experienced as the recoat assembly200 traverses the build area 124 to distribute material for the currentlayer and/or any other type of expected force to be experienced as therecoat assembly 200 traverses the build area 124 to distribute materialfor the current layer), a comparison between the expected pressure ormeasured force profile and the measured force or pressure may be made,and an action may be taken in response to the comparison.

At step 2608, the method comprises adjusting the at least one operatingparameter of the additive manufacturing system 100 in response to thedetermined first force. For example, in some embodiments, the at leastone operating parameter of the additive manufacturing system 100 isadjusted based on a comparison of an expected force on the first roller202 to the first force on the first roller 202 determined based on thefirst output signal of the first sensor. In embodiments, when adeviation beyond a given threshold is determined to have occurred, acorrective action may be taken, such as to adjust a recoat traversespeed for the current layer, adjust a roller rotation speed for thecurrent layer, adjust a recoat traverse speed for one or more subsequentlayers, adjust a roller rotation speed for one or more subsequentlayers, adjust a height of one or more rollers for the current layerand/or for one or more subsequent layers, etc.

In some embodiments, when an expected pressure or force deviates from ameasured pressure or force during spreading of material for a currentlayer by the recoat assembly 200, the layer recoat process may bedetermined to be defective. The extent of force deviation may be used todetermine a type of defect (e.g., a powder defect, a recoat rollerdefect, insufficient binder cure, a jetting defect, or the like.

In embodiments, each of steps 2602-2608 may be performed, for example,by the electronic control unit 300. As noted above, in embodiments, theelectronic control unit 300 may include one or more parameters foroperating the additive manufacturing system 100. By adjusting at leastone operating parameter in response to determined forces acting on thefirst roller 202 (FIG. 6B), the electronic control unit 300 may activelyadjust operation of the additive manufacturing system 100. As oneexample, in embodiments, the at least one parameter of the additivemanufacturing system 100 includes a speed with which the recoat assemblytransverse actuator 144 moves the recoat assembly 200 relative to thebuild area 124, as outlined above.

In some embodiments, the at least one parameter is a speed of rotationof the first rotational actuator 206. In embodiments, upon determining aforce acting on the first roller 202 below a configurable threshold, theelectronic control unit 300 may direct the first rotational actuator 206to decrease the speed at which the first rotational actuator 206 rotatesthe first roller 202. For example, the determination of comparativelylow force or forces acting on the first roller 202 may be indicativethat the speed at which the first rotational actuator 206 may be reducedwhile still being sufficient to fluidize the build material 31. Bycontrast, upon detecting a force acting on the first roller 202exceeding a configurable threshold, the electronic control unit 300 maydirect may direct the first rotational actuator 206 to increase thespeed at which the first rotational actuator 206 rotates the firstroller 202. For example, the determination of comparatively high forceor forces acting on the first roller 202 may be indicative that thespeed at which the first rotational actuator 206 is rotating the firstroller 202 is insufficient to fluidize the build material 31 as desired.

In some embodiments, the at least one parameter is a target thickness ofa subsequent layer of build material 31 and/or the layer of buildmaterial 31 being distributed. In embodiments, upon determining a forceacting on the first roller 202 below a configurable threshold, theelectronic control unit 300 may direct the recoat assembly 200 toincrease a target thickness of a subsequent layer of build material 31,for example by changing the height of the recoat assembly 200. Forexample, the determination of comparatively low force or forces actingon the first roller 202 may be indicative that the thickness of thelayer of build material 31 distributed by the recoat assembly 200 may beincreased. By contrast, upon detecting a force acting on the firstroller 202 exceeding a configurable threshold, the electronic controlunit 300 may direct the recoat assembly 200 to decrease a targetthickness of a subsequent layer of build material 31, for example bychanging the height of the recoat assembly 200. For example, thedetermination of comparatively high force or forces acting on the firstroller 202 may be indicative that the thickness of the layer of buildmaterial 31 distributed by the recoat assembly 200 should be decreased.

In some embodiments, the method illustrated in FIG. 26 further comprisesdetermining a type of defect. For example, in some embodiments, a typeof defect may be determined based on a comparison of an expected forceon the first roller 202 and the first force on the first roller 202. Forexample, a defect in the build material 31 may be associated with aparticular amount of force applied to the first roller 202, while adefect in the first roller 202 may be associated with a different amountof force applied to the first roller 202. Accordingly, the amount offorce applied to the first roller 202 may be utilized to determine atype of defect within the additive manufacturing system 100.

In embodiments, the adjustment of the at least one operating parameterof the additive manufacturing system 100 can be implemented at one ormore times during a build cycle. For example, in embodiments, the atleast one operating parameter may be adjusted while the layer of buildmaterial 31 is being distributed by the recoat assembly 200. In someembodiments, the at least one operating parameter of the additivemanufacturing system 100 is adjusted when a next layer of build material31 is distributed by the recoat assembly 200.

In some embodiments, a wear parameter may be determined based on thedetermined first force. For example, as the first roller 202 wears, forexample through repeated contact with the build material 31, thediameter of the first roller 202 may generally decrease. The decreaseddiameter of the first roller 202 may generally lead to lower forces onthe first roller 202 as the first roller 202 distributes build material31.

In some embodiments, wear on other components of the recoat assembly 200may be determined based on the determined first force. For example, thefirst roller 202 may be coupled to the base member 250 (FIG. 3) via oneor more bearings, or the like. Additionally and as noted above, thefirst roller 202 may be coupled to the first rotational actuator 206(FIG. 3) through a belt, a chain, or the like. Wear on the one or morebearings and/or the belt, chain, or the like may generally lead toincreased forces on the first roller 202. In some embodiments, theincreased forces on the first roller 202 may be determined by thecurrent sensor 306.

In some embodiments, the method depicted in FIG. 26 further includesreceiving a second output signal from a second sensor mechanicallycoupled to and in contact with the second roller support 212. Inembodiments, the second sensor may include any of the first strain gauge240A, the second strain gauge 240B, the load cell 242, and/or theaccelerometer 244. In embodiments, the method further includes receivingthe second output signal from the second sensor as the layer of thebuild material 31 is distributed on the build area 124 with the recoatassembly 200 and determining the first force on the first roller 202based on the first output signal of the first sensor and the secondoutput signal of the second sensor.

In some embodiments, the method depicted in FIG. 26 further includesreceiving a third output signal from a third sensor mechanically coupledto and in contact with the third roller support 216. In embodiments, thethird sensor may include any of the include any of the first straingauge 240A, the second strain gauge 240B, the load cell 242, and/or theaccelerometer 244. In embodiments, the method further includes receivingthe third output signal from the third sensor as the layer of the buildmaterial 31 is distributed on the build area 124 with the recoatassembly 200 and determining a second force on the second roller 204based on the third output signal of the third sensor. In someembodiments, the method further includes adjusting the at least oneoperating parameter in response to the determined first force and thedetermined second force. In this way, the at least one operatingparameter may be adjusted based on determined forces acting on both thefirst roller 202 and the second roller 204. For example a detection of adeceleration of the first roller 202 and/or the second roller 204 abovea configurable threshold may be indicative of a collision of the recoatassembly 200 with an object, such as a foreign object within theadditive manufacturing system 100. By detecting a collision, operationof the additive manufacturing system 100 may be halted to preventfurther damage to the additive manufacturing system 100, and/or providean indication to a user that maintenance is necessary.

In some embodiments, the method depicted in FIG. 26 further includesdetermining a collision of the recoat assembly 200. For example, in someembodiments, the method further includes determining a roller collisionevent based on an output of the at least one accelerometer 244, anadjusting the at least one operating parameter when the roller collisionevent is determined to have occurred.

Referring to FIGS. 24, 27, and 28, a method for forming an object isschematically depicted. In a first step 2702, the method comprisesmoving the recoat assembly 200 over the supply receptacle 134 in acoating direction, as indicated by arrow 40. The supply receptacle 134comprises build material 31 positioned within the supply receptacle 134,and the recoat assembly 200 comprises a first roller 202 and a secondroller 204 that is spaced apart from the first roller 202. As notedabove, in some embodiments, the recoat assembly 200 may include only asingle roller. In a second step 2704, the method comprises rotating thefirst roller 202 of the recoat assembly 200 in a counter-rotationdirection 60, such that a bottom of the first roller 202 moves in thecoating direction 40. In the embodiment depicted in FIG. 28, thecounter-rotation direction 60 is shown as the clockwise direction. In athird step 2706, the method comprises contacting the build material 31with the first roller 202 of the recoat assembly 200, thereby fluidizingat least a portion of the build material 31. At step 2708, the methodcomprises irradiating, with the front energy source 260, an initiallayer of build material 31 positioned in the build area 124 spaced apartfrom the supply receptacle 134. As noted above, irradiating the initiallayer of build material 31 may bind the build material 31 to binder 50positioned in the build area 124. Subsequent to step 2708, at step 2710,the method comprises moving the fluidized build material 31 from thesupply receptacle 134 to the build area 124 with the first roller 202,thereby depositing a second layer of the build material 31 over theinitial layer of build material 31 within the build area 124. Subsequentto step 2710, at step 2712, the method comprises irradiating, with therear energy source 262, the second layer of build material 31 within thebuild area 124. In some embodiments, steps 2708-2712 may occur within apredetermined cycle time. For example, in some embodiments, steps2708-2712 may be performed within a range between 5 seconds and 20seconds.

While the method described above includes moving the recoat assembly 200over a supply receptacle 134, it should be understood that in someembodiments a supply receptacle 134 is not provided, and instead buildmaterial 31 may be placed on the build area 124 through other devices,such as the build material hopper 360 (FIG. 2B).

In embodiments, the electronic control unit 300 may direct variouscomponents of the additive manufacturing system 100 to perform steps2702-2712. In embodiments, by irradiating the initial layer of buildmaterial 31, the front energy source 260 may act to cure binder 50positioned on the build material 31 of the build area 124. Byirradiating the second layer of build material 31, the rear energysource 262 may generally act to pre-heat the build material 31, and/orfurther cure the binder material 50.

By irradiating the build material 31 with a front energy source 260 thatis separate from a rear energy source 262, the intensity of energyemitted by the recoat assembly 200 may be distributed, as compared torecoat assemblies including a single energy source, which may reducedefects in the binder 50 and/or the build material 31. Moreparticularly, the thermal power density of a single energy sourceheating system can quickly reach a limit due to space and costconstraints. Excessive power output in a single energy source heatingsystem can be detrimental to the quality of the cure of the binder 50 ineach layer of build material 31, as large spikes in temperature mayinduce stress and cracks in the relatively weak parts and can causeuncontrolled evaporation of solvents within the binder 50. By includingthe front energy source 260 and the rear energy source 262, the thermalpower intensity of the recoat assembly 200 may be distributed. Inparticular and as noted above, including multiple energy sources (e.g.,the front energy source 260 and the rear energy source 262), energy canbe applied to build material 31 (FIG. 1A) over a comparatively longerperiod of time as compared to the application of energy via a singleenergy source. In this way, over-cure of build material 31 bound bycured binder 50 can be minimized.

Furthermore, because the recoat assembly 200 includes the front energysource 260 and the rear energy source 262, operation of the recoatassembly 200 may be maintained in the case of failure of the frontenergy source 260 or the rear energy source 262. In particular, byproviding multiple energy sources (e.g., the front energy source 260 andthe rear energy source 262 and/or other additional energy sources), inthe case of failure of one of the energy sources, the other energysource may continue to be utilized, so that the recoat assembly 200 maycontinue to operate, thereby reducing downtime of the recoat assembly200.

The first roller 204, in embodiments, is rotated at a rotational speedsufficient to fluidize at least a portion of the build material 31. Insome embodiments, the first roller 204 is rotated at a rotational speedof at least 2.5 meters per second. In some embodiments, the first roller204 is rotated at a rotational speed of at least 2 meters per second. Insome embodiments, the first roller 204 is rotated at a rotational speedof at least 1 meter per second.

In some embodiments, the operation of the front energy source 260 and/orthe rear energy source 262 may be controlled and modified. Inembodiments, the front energy source 260 and/or the rear energy source262 may be communicatively coupled to the electronic control unit 300through one or more relays, such as solid state relays, that facilitatecontrol of the front energy source 260 and/or the rear energy source262.

In some embodiments, the additive manufacturing system 100 may include atemperature sensor 286 communicatively coupled to the electronic controlunit 300. The temperature sensor 286 may include any contact ornon-contact sensor suitable for detecting a temperature of the buildmaterial 31, for example and without limitation, one or more infraredthermometers, thermocouples, thermopiles or the like. As shown in FIG.6A, one or more temperature sensors 286 may be positioned rearward ofthe first roller 202 and/or the second roller 204, however, it should beunderstood that the one or more temperature sensors 286 may be coupledto the recoat assembly at any suitable position. In embodiments,subsequent to irradiating the initial layer of build material 31 withthe front energy source 260 and/or irradiating the second layer of buildmaterial 31, the method further comprises detecting a temperature of theirradiated build material 31 with the temperature sensor 286. In someembodiments, the output of the front energy source 260 and/or the rearenergy source 262 may be adjusted in response to the detectedtemperature of the build material 31 (e.g., feedback control). In someembodiments, the detected temperature may be stored such that theelectronic control unit 300 may develop a model for controlling thefront energy source 260 and/or the rear energy source 262 (e.g.,feedforward control). For example, in some embodiments, the methodfurther comprises changing at least one parameter of the front energysource 260 or the rear energy source 262 based at least in part on thedetected temperature. Further, in some embodiments, at least one ofirradiating the initial layer of build material 31 with the front energysource 260 and irradiating the second layer of build material 31comprises applying a predetermined power to the front energy source 260or the rear energy source 262, and the method further comprises changingthe predetermined power based at least in part on the detectedtemperature.

In some embodiments, the recoat assembly 200 includes a distance sensor288 communicatively coupled to the electronic control unit 300. Thedistance sensor 288 is generally configured to detect a thickness of alayer of build material 31 positioned below the recoat assembly 200. Inembodiments, the electronic control unit 300 may receive a signal fromthe distance sensor 288 indicative of the layer or build material 31moved to the build area 124. The electronic control unit 300 may changeone or more parameters based on the detected thickness of the layer ofbuild material 31 such that the recoat assembly 200 may move buildmaterial 31 to the build area 124 as desired. In embodiments, thedistance sensor 288 may include any sensor suitable for detecting athickness of build material 31, such as and without limitation, a lasersensor, an ultrasonic sensor, or the like.

In some embodiments, the second roller 204 may be positioned above thefirst roller 202 in the vertical direction (i.e., in the Z-direction asdepicted). In these embodiments, only the first roller 202 may contactthe build material 31, and the second roller 204 may act as a spareroller that can be utilized in the case of failure or malfunction of thefirst roller 202.

In some embodiments, the second roller 204 is rotated in a rotationdirection 62 that is the opposite of the counter-rotation direction 60and the second roller 204 contacts the build material 31 within thebuild area 124. The second roller 204 may be rotated at a rotationalvelocity that corresponds to a linear velocity of the recoat assembly200. More particularly, by matching the rotational velocity of thesecond roller 204 to match the linear velocity of the recoat assembly200, the second roller 204 may generally act to compact the buildmaterial 31, while causing minimal disruption to the build material 31as the recoat assembly 200 moves with respect to the build area 124. Inembodiments, the rotational velocity of the first roller 202 is greaterthan the rotational velocity of the second roller 204. In someembodiments, as the second roller 204 compacts the build material 31,the second roller 204 may be positioned lower than the first roller 202in the vertical direction (i.e., in the Z-direction as depicted).

In some embodiments, once the second layer of build material 31 isdeposited the first roller 202 is moved upward in the vertical direction(i.e., in the Z-direction as depicted), such that the first roller 202is spaced apart from the second layer of build material 31. The recoatassembly 200 is then moved to the supply receptacle 134 in a directionthat is opposite of the coating direction 31. In this way, the recoatassembly 200 may be returned to the recoat home position 148 (FIG. 2A).In some embodiments, the recoat assembly 200 is moved to the supplyreceptacle 134 at a return speed. In embodiments the return speed isgreater than a coating speed at which the recoat assembly 200 moves thefluidized build material 31 to the build area 124. In some embodiments,to avoid damaging cured binder the build material 31, the coating speedmay be limited, and accordingly, by increasing the return speed, theoverall cycle time required to deposit build material 31 may be reduced.

In some embodiments, the first roller 202 and/or the second roller 204may compact the build material 31 in the build area 124 as the recoatassembly 200 moves back to the home position 148. For example andreferring to FIGS. 29A and 29B, the recoat assembly 200 is depictedmoving in coating direction 40, and a direction 42 opposite the coatingdirection 40, respectively. In some embodiments, the method furthercomprises rotating the first roller 202 and/or second roller 204 in thecounter-rotation direction 60. Rotating the first roller 202 and/or thesecond roller 204 in the counter-rotation direction 60 may compriserotating the first roller 202 and/or the second roller 204 at arotational velocity that corresponds to a linear velocity of the recoatassembly 200 moving toward the supply receptacle 134.

In some embodiments, before moving the recoat assembly 200 to the supplyreceptacle 134, the method further comprises moving the first roller 202and/or the second roller 204 upward in the vertical direction (i.e., inthe Z-direction as depicted). In some embodiments, the first roller 202and/or the second roller 204 is moved upward between 8 micrometers and12 micrometers in the vertical direction, inclusive of the endpoints. Insome embodiments, the first roller 202 and/or the second roller 204 ismoved upward about 10 micrometers in the vertical direction. In someembodiments, before moving the recoat assembly 200 to the supplyreceptacle 134, the method further comprises moving the first roller 202and/or the second roller 204 upward in the vertical direction (i.e., inthe Z-direction as depicted). In some embodiments, the first roller 202and/or the second roller 204 is moved upward between 5 micrometers and20 micrometers in the vertical direction, inclusive of the endpoints. Bymoving first roller 202 and/or the second roller 204 upward in thevertical direction, the first roller 202 and/or the second roller 204may be positioned to compact the build material 31 in the build area124.

In some embodiments, as the first roller 202 and/or the second roller204 contacts the build material 31 in the build area 124 moving backtoward the supply receptacle 134, the first roller 202 and/or the secondroller 204 is rotated at a rotational velocity that corresponds to thelinear velocity of the recoat assembly 200 moving back toward the supplyreceptacle 134. As noted above, by correlating the rotational velocityof the first roller 202 and/or the second roller 204 to the linearvelocity of the recoat assembly 200, the first roller 202 and/or thesecond roller 204 may compact the build material 31, with minimaldisruption of the build material 31 in the longitudinal direction (i.e.,in the X-direction as depicted).

While FIGS. 29A and 29B include a supply receptacle 134, it should beunderstood that in some embodiments a supply receptacle 134 is notprovided, and instead build material 31 may be placed on the build area124 through other devices, such as the build material hopper 360 (FIG.2B).

In some embodiments, the first roller 202 and the second roller 204 maybe rotated in the counter-rotation direction 60 as the recoat assembly200 moves in the coating direction 40, as shown in FIG. 29C. In someembodiments, the first roller 202 is positioned above the second roller204 as the recoat assembly 200 moves in the coating direction 40. Thefirst roller 202 and the second roller 204 may be rotated in therotation direction 62 as the recoat assembly 200 moves in the returndirection 42, as shown in FIG. 29D. In some embodiments, the firstroller 202 is positioned below the second roller 204 as the recoatassembly 200 moves in the return direction 42. Further, in someembodiments, the front energy source 260 and/or the rear energy source262 may irradiate the build material 31 in the build area 124 as therecoat assembly 200 moves in the coating direction 40 (FIG. 29C) and/oras the recoat assembly 200 moves in the return direction 42.

Referring to FIGS. 24 and 30, an example method for drawing airbornebuild material 31 out of the recoat assembly 200 is schematicallydepicted. In a first step 3002, the method comprises moving the recoatassembly 200 build material 31 in the coating direction 40. At step3004, the method further comprises contacting the build material 31 withthe powder spreading member, causing at least a portion of the buildmaterial 31 to become airborne. At step 3006, the method furthercomprises drawing airborne build material 31 out of the recoat assembly200 with a vacuum 290 in fluid communication with the recoat assembly200.

In embodiments, each of steps 3002-3006 may be performed, for example,by the electronic control unit 300.

In embodiments, the vacuum 290 may draw the airborne build material 31out of the recoat assembly 200 at one or more times during a buildcycle. For example, in some embodiments, the step of drawing airbornebuild material 31 out of the recoat assembly 200 is subsequent to orduring the step of moving the build material 31. Put another way, thevacuum 290 draws the build material 31 out of the recoat assembly 200 atthe end of a build cycle. In some embodiments, the step of drawingairborne build material 31 out of the recoat assembly 200 is concurrentwith the step of moving the build material 31. Put another way, theairborne build material 31 may be drawn out of the recoat assembly 200during the build cycle in a continuous or semi-continuous manner.

In some embodiments, the vacuum 290 may apply a positive pressure to therecoat assembly 200 to dislodge build material 31 accumulated within therecoat assembly 200. For example, in some embodiments, subsequent tomoving the build material 31, the vacuum 290 directs a process gas, suchas air or the like, to the recoat assembly 200. In some embodiments, thevacuum 290 may apply positive pressure while the recoat assembly 200 ispositioned over a drain that applies a negative pressure to collect thebuild material 31. In embodiments, the drain may be positioned proximateto the build area 134 (FIG. 2A).

Based on the foregoing, it should be understood that embodimentsdescribed herein are directed to recoat assemblies for an additivemanufacturing system. In embodiments described herein, recoat assembliesinclude one or more sensors that detect forces acting on the recoatassembly. By detecting forces acting on the recoat assembly, defects maybe identified and one or more parameters related to the operation of therecoat assembly may be adjusted to optimize the performance of therecoat assembly. In some embodiments, recoat assemblies described hereinmay include multiple redundant components, such as rollers and energysources, such that the recoat assembly may continue operation in theevent of failure of one or more components of the recoat assemblies. Insome embodiments, recoat assemblies described herein are in fluidcommunication with a vacuum that acts to collect and contain airbornebuild material.

Further aspects of the embodiments are provided by the subject matter ofthe following clauses:

1. A recoat assembly for an additive manufacturing system, the recoatassembly comprising a base member that is movable in a lateraldirection, a powder spreading member coupled to the base member, whereinthe base member at least partially encapsulates the powder spreadingmember, and a vacuum in fluid communication with at least a portion ofthe base member.

2. The recoat assembly of any preceding clause, further comprising atleast one energy source coupled to the base member.

3. The recoat assembly of any preceding clause, further comprising anagitation device configured to vibrate the recoat assembly.

4. The recoat assembly of any preceding clause wherein the base membercomprises a primary containment housing that at least partiallyencapsulates the powder spreading member and a secondary containmenthousing that at least partially encapsulates and is spaced apart fromthe primary containment housing.

5. The recoat assembly of any preceding clause, wherein the vacuum is influid communication with a cavity defined by the primary containmenthousing and the secondary containment housing.

6. The recoat assembly of any preceding clause, wherein the powderspreading member is a doctor blade.

7. The recoat assembly of any preceding clause, wherein the powderspreading member is a roller rotatably coupled to the base member.

8. The recoat assembly of any preceding clause, wherein the roller is afirst roller, and the recoat assembly further comprises a second rollerrotatably coupled to the base member and at least partially encapsulatedby the base member.

9. The recoat assembly of any preceding clause, wherein the recoatassembly further comprises a cleaning member selectively engagable withat least one of the first roller and the second roller.

10. The recoat assembly of any preceding clause, wherein the cleaningmember comprises a cleaning roller positioned between and engaged withthe first roller and the second roller.

11. The recoat assembly of any preceding clause, wherein the base membercomprises a primary containment housing that at least partiallyencapsulates the powder spreading member.

12. The recoat assembly of any preceding clause, wherein the vacuum isin fluid communication with the primary containment housing.

13. The recoat assembly of any preceding clause, further comprising adiffuser plate positioned between the vacuum and the powder spreadingmember, the diffuser plate defining a plurality of apertures extendingtherethrough.

14. A method for forming an object, the method comprising moving arecoat assembly over a build material a coating direction, wherein therecoat assembly comprises a powder spreading member, contacting thebuild material with the powder spreading member, causing at least aportion of the build material to become airborne, and drawing airbornebuild material out of the recoat assembly with a vacuum in fluidcommunication with the recoat assembly.

15. The method of any preceding clause, further comprising moving buildmaterial over a build area with the powder spreading member, therebydepositing a second layer of the build material over an initial layer ofbuild material.

16. The method of any preceding clause, wherein the step of drawingairborne build material out of the recoat assembly is subsequent to thestep of moving the build material.

17. The method of any preceding clause, wherein the step of drawingairborne build material out of the recoat assembly is concurrent withthe step of moving the build material.

18. The method of any preceding clause, further comprising, subsequentto moving the build material, directing air to the recoat assembly.

19. The method of any preceding clause, wherein the powder spreadingmember comprises a roller and the method further comprises rotating theroller.

20. The method of any preceding clause, wherein contacting the buildmaterial with the roller causes at least a portion of the build materialto fluidize.

21. The method of any preceding clause, wherein drawing the airbornebuild material out of the recoat assembly comprises applying a vacuumpressure to a containment housing that at least partially encapsulatesthe powder spreading member.

22. The method of any preceding clause, further comprising, subsequentto moving the recoat assembly over the build material, directing processgas to the recoat assembly.

23. The method of any preceding clause, wherein directing air to therecoat assembly comprises directing air to a containment housing that atleast partially encapsulates the roller.

24. The method of any preceding clause, wherein directing air to therecoat assembly comprises directing air to at least one of a secondarycontainment housing that is spaced apart from and at least partiallyencapsulates a primary containment housing that at least partiallyencapsulates the roller.

25. The method of any preceding clause, wherein drawing the airbornebuild material out of the recoat assembly comprises applying a vacuumpressure to a secondary containment housing that is spaced apart fromand at least partially encapsulates a primary containment housing thatat least partially encapsulates the at the powder spreading member.

26. The method of any preceding clause, further comprising, irradiating,with a front energy source coupled to an end of the recoat assembly, aninitial layer of build material.

27. The method of any preceding clause, further comprising, subsequentto irradiating the initial layer of build material, moving the fluidizedbuild material to a build area, thereby depositing a second layer of thebuild material over the initial layer of build material.

28. The method of any preceding clause, further comprising collectingthe airborne build material drawn from the recoat assembly, anddirecting the collected build material beneath the recoat assembly.

29. The method of any preceding clause, further comprising vibrating therecoat assembly with an agitation device coupled to the recoat assembly.

30. An additive manufacturing system comprising a recoat assemblycomprising a base member that is movable in a lateral direction, apowder spreading member coupled to the base member, wherein the basemember at least partially encapsulates the powder spreading member, anda vacuum in fluid communication with at least a portion of the basemember, an electronic control unit communicatively coupled to thevacuum, and a build area positioned below the recoat assembly.

31. The additive manufacturing system of any preceding clause, whereinthe build area comprises a build receptacle positioned below the recoatassembly.

32. The additive manufacturing system of any preceding clause, furthercomprising a supply receptacle spaced apart from the build area.

33. The additive manufacturing system of any preceding clause, furthercomprising a build material hopper.

34. The additive manufacturing system of any preceding clause, whereinthe electronic control unit directs the vacuum to draw build materialout of the recoat assembly.

35. The additive manufacturing system of any preceding clause, whereinthe base member comprises a primary containment housing that at leastpartially encapsulates the powder spreading member and a secondarycontainment housing that at least partially encapsulates and is spacedapart from the primary containment housing.

36. The additive manufacturing system of any preceding clause, whereinthe vacuum is in fluid communication with the secondary containmenthousing.

37. The additive manufacturing system of any preceding clause, furthercomprising a recoat assembly transverse actuator coupled to the basemember and communicatively coupled to the electronic control unit.

38. The additive manufacturing system of any preceding clause, whereinthe electronic control unit directs the recoat assembly transverseactuator to move the base member in the lateral direction to move buildmaterial with the powder spreading member, thereby depositing a secondlayer of the build material over an initial layer of build materialpositioned in the build area.

39. The additive manufacturing system of any preceding clause, whereinthe electronic control unit directs the vacuum to draw airborne buildmaterial out of the recoat assembly while directing the recoat assemblytransverse actuator to move the build material.

40. The additive manufacturing system of any preceding clause, whereinthe electronic control unit directs the vacuum to draw airborne buildmaterial out of the recoat assembly concurrently with directing therecoat assembly transverse actuator to move the build material.

41. The additive manufacturing system of any preceding clause, whereinthe electronic control unit, subsequent to directing the recoat assemblytransverse actuator to move the build material, directs the vacuum todirect air to a primary containment housing that at least partiallyencapsulates the powder spreading member.

42. The additive manufacturing system any preceding clause, wherein thepowder spreading member comprises a roller.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

1. A recoat assembly for an additive manufacturing system, the recoat assembly comprising: a base member that is movable in a lateral direction; a powder spreading member coupled to the base member, wherein the base member at least partially encapsulates the powder spreading member; and a vacuum in fluid communication with at least a portion of the base member.
 2. The recoat assembly of claim 1, further comprising an agitation device configured to vibrate the recoat assembly.
 3. The recoat assembly of claim 1, wherein the base member comprises a primary containment housing that at least partially encapsulates the powder spreading member and a secondary containment housing that at least partially encapsulates and is spaced apart from the primary containment housing.
 4. The recoat assembly of claim 3, wherein the vacuum is in fluid communication with a cavity defined by the primary containment housing and the secondary containment housing.
 5. The recoat assembly of claim 1, wherein the powder spreading member is a doctor blade.
 6. The recoat assembly of claim 1, wherein the powder spreading member is a roller rotatably coupled to the base member.
 7. The recoat assembly of claim 6, wherein the roller is a first roller, and the recoat assembly further comprises a second roller rotatably coupled to the base member and at least partially encapsulated by the base member.
 8. The recoat assembly of claim 7, wherein the recoat assembly further comprises a cleaning member selectively engagable with at least one of the first roller and the second roller.
 9. (canceled)
 10. A method for forming an object, the method comprising: moving a recoat assembly over a build material a coating direction, wherein the recoat assembly comprises a powder spreading member; contacting the build material with the powder spreading member, causing at least a portion of the build material to become airborne; and drawing airborne build material out of the recoat assembly with a vacuum in fluid communication with the recoat assembly.
 11. The method of claim 10, further comprising moving build material over a build area with the powder spreading member, thereby depositing a second layer of the build material over an initial layer of build material.
 12. The method of claim 10, wherein drawing the airborne build material out of the recoat assembly comprises applying a vacuum pressure to a containment housing that at least partially encapsulates the powder spreading member.
 13. The method of claim 10, further comprising, subsequent to moving the recoat assembly over the build material, directing process gas to the recoat assembly.
 14. The method of claim 10, wherein drawing the airborne build material out of the recoat assembly comprises applying a vacuum pressure to a secondary containment housing that is spaced apart from and at least partially encapsulates a primary containment housing that at least partially encapsulates the powder spreading member.
 15. The method of claim 10, further comprising, irradiating, with a front energy source coupled to an end of the recoat assembly, an initial layer of build material.
 16. The method of claim 15, further comprising, subsequent to irradiating the initial layer of build material, moving the fluidized build material to a build area, thereby depositing a second layer of the build material over the initial layer of build material.
 17. An additive manufacturing system comprising: a recoat assembly comprising: a base member that is movable in a lateral direction; a powder spreading member coupled to the base member, wherein the base member at least partially encapsulates the powder spreading member; and a vacuum in fluid communication with at least a portion of the base member; an electronic control unit communicatively coupled to the vacuum; and a build area positioned below the recoat assembly. 18-20. (canceled)
 21. The additive manufacturing system of claim 17, wherein the electronic control unit directs the vacuum to draw build material out of the recoat assembly.
 22. The additive manufacturing system of claim 17, wherein the base member comprises a primary containment housing that at least partially encapsulates the powder spreading member and a secondary containment housing that at least partially encapsulates and is spaced apart from the primary containment housing.
 23. The additive manufacturing system of claim 17, further comprising a recoat assembly transverse actuator coupled to the base member and communicatively coupled to the electronic control unit, wherein the electronic control unit directs the recoat assembly transverse actuator to move the base member in the lateral direction to move build material with the powder spreading member, thereby depositing a second layer of the build material over an initial layer of build material positioned in the build area.
 24. (canceled)
 25. The additive manufacturing system of claim 23, wherein the electronic control unit directs the vacuum to draw airborne build material out of the recoat assembly while directing the recoat assembly transverse actuator to move the build material. 